almost99

I have a stock motor with stock sequential turbo set up. I also have a PFS FMIC, a PFS intake, down pipe, high flow cat, cat back, e-fini ypipe, high flow fuel pump, and Power FC computer. In second gear primary boost reaches and holds it set point, but after the secondary turbo kicks in, it reaches it set point then drops off 2 PSI. In third gear the same thing happens, but only drops 1PSI. I've got silicon hoses throughout the turbo control system, and I verified that the Turbo control actuator is getting both vacuum and pressure after 4500 RPM. I've also verified that the charge control valve and charge relief valve are functioning (when removed), but I haven't T'd into the line while driving yet. Also, it may not be related, but if I go above 4500 RPM at WOT, let off the gas and let the RPM drop to around 2500 and punch it again, it feels like my secondary turbo is online and boost is slow to build until after 4500 RPM.

Any Ideas on where to look next?

zayrx7

check under the manifold for a loose holes that may have come off. look towards the front.

almost99

I've removed the extension manifold, tested all solonoids and check valves, and verified hose connections and routings. It is not anything as obvious. I'm looking for some theorys and a test method for proving the theory.

technonovice

You checked the IC hoses for leaks? Intake elbow o-ring? Throttle body gasket?

almost99

I put in an e-fini y-pipe, replaced the two IC couplers (and made sure they were clamped tight). I replaced the o-ring this weekend. None of these has helped.

I'll put the throttle body gasket on the list of things to try.

Since my original post, I tested the CRV contol line while driving and it provides consistant boost after 4500. I tapped into the charge control valve control line and added a tap to the secodary turbo to take measurements tomorrow.