I have 3" down pipe and catback with stock cat, PFC, air intake and a front mount intercooler. I am also running stock twins seq. I get good boost til the transition at 4500 rpm then I get no boost. I drove the car the other day and noticed that in second gear at wot it held 7 psi after 4500 rpm then slowly dropped off. When I shifted to 3rd there was 0 psi again.
Where should I start?
Thanks

 

your gonna have to dive into the rats nest and check the pre-control solenoid.... i believe thats the usual suspect in secondary boost issues.

i would also venture to check the CCA in the y-pipe.... i had a problem where i get good boost after transition and then boost would fall off dramatically by redline, and this was intermittent.
I came to the conclusion that the CCA butterly would get stuck open sometimes

 

Read through the FAQ and go through the troubleshooting steps, there's tons of things that could be the issue. Anything that anyone posts on what the problem could be is just a random guess. You're gonna have to go in there and start testing things that cause secondary boost problems as per the FAQ.

 

try checking your vacuum, is it at about 14 LBS at Idle you might have a split hose on you turbo,or some where else ,try listing for a leak some were or just slowly spray your engine with a water to see if it stumbles then look in that area.for the cracked one valve,or bad hose ,if you do not get a stumble, it may be electrical controls, or............... a mechanical issues with your turbos ,.................ps when spraying, don't spray any water at the air filters

 

check for vacuum leaks. Most likely turbo control solenoids under manifold or precontrol/wastgate solenoids in the front. A clogged cat can also bring down boost. but first things first, check out the leaks, then solenoids with a vacuum pump. the faq is great help.

 

I started off by getting under the car and checked the c clips on the actuators. They were good. Next I removed the upper intake manifold hoping to see a vacuum line off. No such luck, all the vac lines appear to be in place and I can't find any cracks or any damage.So I then started looking around the turbos, with no luck. So I start the car and cold idle is a little high, after it warmed up the idle started bouncing between 1k to 1.5k back and forth. I must have missed a vac line while reassembling the upper and throttle body.
I am considering going simplified seq or even full non seq.
Any suggestions?

 

If the idle problems weren't happening before then you most likely forgot to tighten something down properly and you're getting a leak. Re-trace everything you removed to make sure they're tightened properly and in the right place.

Did you test the solenoids when you removed the UIM? That's really the main thing you should've done when you were in there aside from checking the vacuum lines themselves.

If you don't have a mityvac to test them then I'd say now's the time to get one.

 

many suspects here. Charge control solenoid line off..... Broken check valve into pressure chamber in front of manifold. Charge control valve sticking open or blown secondary turbo....which is very possible! Just happened to me at the track last weekend! Bad rebuild by previous owner!

 

In hind sight of my old secondary problem, i would suggest starting from the outside and work your way in. Start with the turbo to y-pipe connection, crv,bov, intercooler flex sections ect