My car has been backifring throught the intake lately, its mostly noticable when its warmed up , and under load, only occasionally while its in park, and you blip the throttle does it backfire. It also runs like crap, unless its stone cold. after a minute or two. its sput sput sput bam, sput sput sput bam bam bam. its like timing is so far advanced the spark is coming before the intake valve closes. could the Opti cause this? anything else. motor is brand new valve lash is set good. Anybody seen this??

 

Backfires are from 3 things valve timing, spark timing or lean conditions.

Since it's good for 2 minutes then goes to S@#$, I'm leaning (no pun intended) with lean. At this point I have more questions than answers. Tell us about the engine. How many horse power is it estimated to be putting out? What fuel pump and regulator are you using? what filter are you using? Have you flow matched the new injectors and have you picked the right size? I could go on and on.

Did you pick the right size dowel pin on the cam for the distributor your using?

Who put the valve train together and timed it?

Have you checked the fuel pressure and basic things like compression and so on? Have you broken the engine in like it's supposed to be done?