I having an issue I can’t figure out, and I’m open to any advise. I have a 2.4 with a twin scroll GT4088 TS that is not spooling until about 6,000 rpm. It used to spool around 4,700 rpms and I can’t seem to pin down what’s changed. I recently rebuilt my clinderhead and replaced my water pump.

So far I’ve done a compression test was great 170-175 psi across the board. A boost leak test, only two real tiny small leaks (probably there the whole time). The wastegates only open at full boost and the turbo seems fine (wheel spins great, very little shaft play)

All I can think of is an exhaust leak or some other issue with the turbo. Any thoughts???

 

What PSI are the gates cracking at?

 

I would start by checking all the gaskets before the turbo and make sure they aren't blown and leaking exhaust and make sure the manifold to head is torqued and manifold to turbo is as well.

What boost controller, wastegates are you using that might help us. Also if u havvent already check all the vacuum lines over thoroughly.