95 K2500 Low Power, Misses some under load (when Cold)

I have a 1995 K2500 That had a leaking TBI unit, I replavced the complete TBI Unit with the one from holley. The truck has hardly any power when cold, and cuts out (misses) really bad. It has a 5.7 liter motor, and my mgp is around 10mpg. I have also developed some whitish film around the exhaust pipe on my stainless steal accent pieces.