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Nothing else on the turbo install will determine how well the car runs more than the placement of the VAF.  We all know how sensitive it is and thus true and accurate measurements and proper orientation are crucial. 

I basically put the intake and VAF in like it was when I received the turbo since I finished up at 2am and wasn't able to fabricate a new intake at the time.   The nice aluminum intake pipe with the HKS blow-off valve was attached between the turbo and throttle body and the VAF was placed before the inlet of the turbo. 

A pipe curved from the inlet of the turbo back toward the engine bay (see right) and then down along the side of the inner fender well (see below).  The VAF was then attached to this pipe and hung straight down with the filter on the end.

When I first started the car with it connected this way, the tach immediately shot to 2000 and then it died.  I tried again, but found I needed to hold the accelerator down for a fast idle in order for it not to stop running.

I did drive it like this since I needed to run the car 30-60 minutes still to cure the Black Satin on the exhaust pipes.  This stuff did smoke profusely and it took a few minutes for me to convince myself it wasn't something detrimental that I installed wrong.  The car drove OK and boosted fine, but try to push in the clutch or stop at a light and the car would just completely die.  I honestly cannot see how the car was ever driveable with the VAF like this.

I got the exhaust pipes cured and then got some well-deserved sleep to start fresh the next day.  My project was to relocate the VAF in order for it to be in a horizontal rather than vertical position.  This was my intent from the very beginning as was it to move it after the turbo.  More on that later.

For now, I rigged up another pipe (yes, PVC) from the inlet of the turbo that curved back towards the motor just like the previous one did.  However, instead of turning downward, I put the VAF straight across (actually about a 10° angle up) over the starter.   This took a little fudging as the space is really tight and the VAF is rather large.  After an hour or so, I got the VAF in with the filter attached.

The car ran much better this way...or I should say that it ran, period.  The car was actually able to idle by itself and driveablility was restored. 

There was a little roughness to the idle like the car had a cam or was missing a cylinder, but compared to the having the VAF vertical, it might as well have been a Lexus motor with 10 miles on it.

I drove the car this way for a few days before I noticed the bottom rubber part of the K&N filter beginning to disfigure from the heat.  I also did have 2 minor backfires during this time.

As I mentioned, I wanted to place the VAF after the turbo so that the IAT (Intake Air Temperature) sensor could send the proper readings to the ECU.  With the VAF in front of the turbo, the ECU is getting readings of cool air and advancing the timing.  In effect, the motor is getting much hotter air which would require a timing retard (or at least not such a severe advance).  I am theorizing that is what caused the backfires.

Before having an intake fabricated to hold the VAF between the turbo and throttle body, I did want to ensure that it would function properly so I made one up myself.  

Using some Mustang tailpipes that I had laying in the garage (don't ask) and various reducers and connectors, I cut a few bends and made a pretty shabby intake pipe to hold the VAF.  As you can see in this rather dim photo, I purchased a sheet of heat shielding and wrapped the VAF.

Unfortunately the air filter did not fit on the turbo with the space available, so a smaller one will be ordered.  On a lighter note, the extremely smooth idle returned with this setup.  No bounce or skip.  Spool time dropped and the suction sound that turbos are famous for increased substantially.  My hypothesis on these are that 1) the IAT is supplying the readings for air that the motor is actually getting (no backfires to date with this setup), 2) the turbo spools sooner because there is no restriction on the inlet to draw air through (VAF and piping).

The car is simply much better running and faster with the VAF after the turbo.   The one drawback is that I have lost the BOV temporarily.  I have yet to experience any compressor surge, but I will be having the GReddy Type-S BOV installed this week anyway.  The one problem with my "homemade" intake was the silicone connectors and pipes.  The connectors would get rather pliable with the heat and the pipes had no beads on the ends so after a few hard jaunts, I would end up blowing a pipe off either the VAF or the throttle body.  I had to stop and re-insert the pipes on several occasions in the few days I used this intake.

After a few days of problem-free driving and several rather impressive victories on the road, I decided that this setup was the permanent solution.   I had new pipes bent up by Certified Muffler that are larger than the original pipes and that would hold together under pressure. 

The pipes on this intake are aluminized steel that I high-temp painted "Aluminum".   Pipe from the turbo outlet to the front of the VAF is 2-1/2" (as opposed to the original intake pipe of 2" OD) that was stretched to 3" in order to fit snuggly over the front of the VAF.  The tube from the rear of the VAF to the throttle body is 3".

In addition to fitting better, the pipes also have the ends flared so they will not slip past the clamps.  The silicone connectors have been trashed in lieu of 5-ply nitrile connectors/reducers.  The GReddy BOV will be fitted onto the pipe between the turbo and the front of the VAF.

I have had several days of 9psi driving on this intake without a BOV and have yet to blow a pipe off so I suppose it's on for good. 

As I mentioned above, the K&N filter that I had did not fit on the inlet of the turbo.  In order to keep at least any large objects from entering the turbo and motor, I made a screen out of mesh that I purchased at the local home improvement store.

I cut it to fit and then attached it to the turbo with a band clamp.  I definitely don't suggest driving like this for a long time as dust and particles are still able to get in.   This may be a nice option for the track however as all inlet-side restrictions are nil.

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