New to this forum, but I have an 06 s.e Evo 9 and I have full turbo back exhaust and intake...got it tuned at turbo Trix in jersey and 3rd and fourth gear peak but then don't hold the boost 1,2 and 5 th are fine. Any thoughts...I'm thinking it's the boost controller I have

 

have you done a boost leak test? start there. that might be the problem

 

I haven't tried it only because I figured if it was a boost leak none of the gears would hold boost? But I'll look into that. The guy who tuned the car said the turbo xs boost controller was ****ty which I figured too but it was on the car when I bought it, I ordered a Hallman

 

hallman is good.. do you know how much boost are you spiking at and how much is it dropping? wouldnt hurt to just check all the vacuum lines to see if one popped or two.
just do a boost leak test and have peace of mind. if you havent replaced your throttle body seals you should do so. i think they start leaking at 24psi

 

I'm at 23 psi and it will drop to 20, but only in 3rd n 4th so hopefully I can resolve the issue..I mean the car drives fine it's just something I noticed and it bothers me..thanks for the advice

 

Definitely do a boost leak test. I had leaks at the throttle body seals, the injector seals, the hose that connects to the wastegate, and my stock diverter/blowoff valve leaked. Also make sure none of your EGR hoses popped off. There are a bunch of EGR hoses behind the motor that don't have clamps from the factory. They are known to pop off. I ziptied all of mine (some are a pretty difficult to get to, but it can be done)

 

Add another to the list with TB seals that leaked. First boost leak test I did, the TB seals started to leak around 16psi. I was losing 4-5 psi because of those two little seals. Fixed that, car pulled harder than the day I bought it.

Just did another test, took it up to 26psi, found an injector seal leaking at 26psi.

You can build a tester for under 5 bucks in parts from a home improvement store, takes all of a half n hour to test. Totally worth it, IMHO.

 

My car presently has a boost leak at the #1 injector. It holds boost in 1st and 2nd, but 3-5 it fluctuates a bit. I notice that if I'm accelerating hard, it does it much less. I believe this is because the system is simply flowing more air through it more quickly. I see the fluctuation in the higher gears under less rapid acceleration because the system is remaining pressurized for longer. This is just a theory. I'm waiting for my injector seals to get here and I'll find out soon enough. Short version: it's possible to see the symptoms of a boost leak only under specific conditions. The leak will slowly get worse and the problem will present itself more consistently (again, just my thinking).