So here is the story, I have been restoring a 88 grand waggy and I am having trouble with the engine. Specs are stock bore, heads ported and polished three angle valve job, 27 thou off heads (est 9-1 comp ratio). Performer Edelbrock intake, 0-5500 Edelbrock cam, shorty headers, single 3 inch exhaust. DUI ignition, live wires, champion plugs, Howell EFI. Problem is it runs like crap, backfiring through intake, stumble poor idle, dies idling. I have checked timing, there does not appear to be any vacuum leaks. I do however have what I think is low vacuum at idle 8-10HG and the needle is bouncy, bring it up to 1800-2500 its's about 15-19HG. When I ease off it goes up slightly and then drops back to 8-10. If it's idling and i punch it I get the backfire or if I load the engine up, again backfire. Any ideas?
Thanks