R34 Gtt Boost Drops Off - Is This Normal Or Do I Have An Issue?

[colossus]

Having the following issue occur (boost dropping off) - I just wish to know wether it is normal or wether I need to upgrade something or have a problem I need to fix.

Car is an R34 GTT tiptronic auto.

Mods:

Turbotech boost tee set at 12psi (aftermarket boost gauge)

HKS cat back exhaust.

Now it dosn't matter wether you have the gearbox in "D" or wether you use the tiptronic, mash the pedal and boost jumps straight up to 12 psi (which is what I want) then drops almost instantly to 10psi, holds it for maybe 2 seconds or thereabouts before dropping off and changing gear. Car feels strong the whole time whilst accelerating (no misfires) but you do get a big backfire as it hits the redline and changes gear (but I have heard this is common in skylines) and probably unrelated.

Planned mods in the near future are dump/front pipe, hiflow cat, FMIC and SAFCII.

Thanks for any advice.

Edited April 18, 2008 by colossus

[Magic]

In an auto, even with just a cat back mod you will get backfire without fail when it shifts gear as it hits the redline.

[colossus]

bump anyone?

[blitza]

It could be a slight boost leak somewhere...thats an option

[Pal]

normal with tee. mine spikes to 12 psi then drops of to 10psi at end rev range. only a electronic will stay stable. front/dump will help

Edited April 18, 2008 by Pal

[R31Nismoid]

1. Sounds like a poor boost controller or install causing it to fall off

2. Needs a tune ideally anyhow

3. Needs a dump pipe also, this will help #1 a bit also

Sounds normal for the basic DIY mate, nothing is drastically wrong

[Yo-Yo]

It's probably the stock turbo if you're still running it.

will hold 12 psi for a bit then tail end off to 9-10 psi through the rev range

[colossus]

cheers guys - appreciate the help. I will post a pic of where we installed the boost tee to ensure its in the right spot.