The car is not stock at all, but has been driving very nicely since install of nearly new JCW motor, JMTC E45HP turbo, catless DP, big FMIC, AP stage 3, and DDMworks intake.

Had a bit of rough idle right after install, but that cleared up with tightening some boost pipes. 1500 miles on motor/turbo combo over about 3 months of aggressive urban driving with no issues after idle cleared up.

This morning I got on it hard to merge onto highway, and the "engine malfunction, reduced power" screen popped up on the dash. warning disappeared, and the car drives smoothly, but there is no power and the exhaust is noticeably louder.

I used the AP to log boost and saw a max of 1.6 PSI, so basically nothing. There is no BOV noise or fluttering like usual from the motor. MPGs are about 21 (normally 23-26 in town).

Reflashed back to stock, still no boost or any new codes or warnings. Wanted to check for issues with wastegate vacuum line, so pulled it at idle -- there is a small bit of vacuum, but haven't measured it.

Any ideas of where to go next?

Car is '07, engine is out of '11 JCW.

 

If you're running the stock DV, I'd pull that and check to make sure it hasn't broke. It's a known weak point especially when running higher boost levels, but even at stock boost.

 

I had to catch a flight this morning and won't be back for a week to mess with it, but I did manage to squeeze my hand under the turbo this morning while it was cool and jiggled the wastegate actuator rod. It sounded like shaking a keychain and had a lot of play. Arric at JM Turbo Coopers thinks that the preload adjustment nuts may have come loose.

I regretfully reinstalled the factory heat shield, so It will take awhile to get into there and really get a look at it, but it's my best theory at this point, that the waste gate is just flapping open and dumping exhaust and preventing any boost from building.