Hi guys recently had the engine rebuilt new rings shells head skim and block decked and have run the car in now not used boost, now since this has been done the boost gauge stays on -30 even when car is running on turned off only goes into boost when accelerating soon as foot comes off it goes into negative boost again, also seems to only boost up to 5psi use to go to 12 am I missing something does anyone have any ideas please

 

Gauge should indeed be in negative numbers when engine is running and your off the throttle, as it is reading vacuum (Air being sucked into the cylinders) and jump to positive when you are on throttle and the boost builds up, first filling the vacuum and then adding pressure on top of that. Many things could be wrong here if it acts weird, first to check should be the gauge itself and if it has been properly connected, leaks, etc.

 

Most likely a boost leak. I’d check the inlet side of things to eliminate that first of all.