Very Odd Engine Issue, Not An Easy One

[cham]

Ok, I bought my 69 Camaro 2 years ago with a crate 350 in it. Not the best crate motor ever but it does have 4 bolt mains. Anyway, on rare occcasions, about every 4 to 6 months (weekend driving only) during warm up <150* I will hear a small back fire. When it does the engine drops about 4 or 5 cylinders and barely stays alive with half throttle. Most times it will stall out. When I go to restart it the engine sounds diffrent while trying to crank it. It starts constantly backfiring and running on just a few cylinders.

If I can keep it running it takes about one or two minutes of spitting and backfiring and everything comes back online and runs perfect. I smell alot of fuel in the exhaust during that time for obvious reasons. While she is hot the engine never backfires or does anything like this. Only on occasion when its cold. I think the amount of time I allow it to warm up has alot to do with it but it seems like an odd thing to happen. I know that if I try and feed it alot of fuel cold it will most likely happen every time.

It did it to me just a few minutes ago and I didnt allow a warm up. Since having this car I have replaced/added the following

Weind 144 blower (12 lbs boost)
Headers/exhaust
Demon Carb
MSD Pro billet dist
MSD 6AL
MSD coil
New Mechanical fuel pump


I thought it might be a ignition issue but since replacing almost every engine bolt on that there is I am left scratching my head.

Any ideas?