[formulabird428]

Car had been running great for years, now is backfiring intermittently through the exhaust and idle is rough. It originally stated out when I was slowly winding the engine out (4000 rpm) and going into second gear.

I have a AFR on the even cylinders, and it didn't seem to indicate an issue during the backfire. I can double check that again.

Engine is completely modified:
Holley elec fuel pump, aero regulator
Holley 950hp
Victor intake
11.25 : 1
KRE 320cfm D Heads
Headers with X-pipe
MSD 6AL with Blaster 2 coil
Solid cam with HS 1.65 rockers


Here are some ideas for the problem and things I'm going to try:

Coil issues, change out
Rockers lash (unlikely, but I'll check)
Bad fuel? Replace? (It's 93 pump, but maybe with COVID the fuel went bad? How long does that take to happen?)
Verify timing


Any else you guys think could be the culprit?

I have a short video clip, I'll see if I can upload it.

Thanks!