bowhunter11

95 camaro z28 lt1
130,000 miles
blew head gaskets at 125,000miles, i sent the head to get machined and valves adjusted, new head gaskets, new oil pressure sensor, new spark plugs.


the vehicle sat for about 2years after we fixed everything. so of course when i finally started it back up from sitting for 2years it had a awful misfire all the time. so i just replaced the opti-spark. started it up and ran great like the day i bought it back in 1996. however i noticed last night at about 40% throttle it has a fairly bad misfire. half throttle, full, none, there is no misfire. just at 40% throttle there is a misfire.

Problem: 40% throttle misfire.

i feel like its a vacuum leak problem but any suggestions?