Doesn't always mean boost leak. My car went into limp mode and would only hit 10psi. I changed out the spark plugs and reset my CEL and i was back to 18psi.

Occasionally my car says it only hits 16psi but the butt dyno says its still good for 18. It started acting up after i put a cheap MBC on it. I plugged the stock solenoid back up and it still acts up. I need to get a Hallman and redo my vacuum lines.

 

I never heard of a "limp mode" on an evo but have for other cars. Did you keep your stock boost solinoid and just bypass it?

 

Well, then mine is special. Anytime the CEL comes on, i get limited to 5psi or 10psi. and then i have a cold start limit to 10psi. the car won't full boost until the car is completely warmed up. No one elses does it to my knowledge.

 

You may want to verify that your turbo's wastegate flapper valve is functioning properly. There have been some cases wherein the integrity of the spot welds which join the flapper valve to the WG's pivot shaft have failed. This results in a constantly open wastegate, and an inability of the turbine wheel to spin the compressor beyond 10PSI.

Also, is your MBC sourced from the compressor housing's discharge nipple, or the intake manifold/diverter valve line? You may want to disconnect the MBC's boost reference at its source, plug it, and run a new and separate hose directly from the compressor housing's discharge nipple to the nipple on the top of the WGA.

Once set up in this manner try increasing boost by rotating the "turnbuckle" on the end of the threaded actuator rod. This will effectively shorten the overall length of the actuator rod which should increase boost by keeing the flapper valve on its seat, if the WG's flapper valve is functioning properly.