on 5.0 1992 mustang I have a boost/vacuum meter has a KB 6 pound on it has been running for 10 years this way OK except when really hot outside(100 or more) then some det. and I back off
When cold, sometimes the meter vacuum (-20 to -10 or so) and then it will spike into boost a few psi and then back down very quickly 1/4 second or so. I think the engine may be backfiring. then when it goes closed loop, it doesn't do it much anymore.
Any other possibilities or ideas on how to fix ?