Honda Civic Engine Question?

[Tom]

this is a reposted question*
I have a 1994 Honda Civic Four door automatic transmission Four cylinder 16valve. I just put a new engine in (myself) and when the engine is revved it skips. It does not matter if the engine is in park reverse neutral or drive it skips and misfires anyway. The engine came from an auto recycling center. I had a carfax done and in 2004 the engine had 57000 miles on it. The civic it came out of was totaled from a collision to the front drivers side. The only thing i had to replace on the engine was the timing cover (it was cracked). I have installed a cold air system and replaced the oil and spark plugs. The car has new headers and a new fuel filter. It also has a new ignition coil. I replaced the timing belt and the engine is perfectly in time. But the engine still misfires. The skipping only occurs when the car is at operating temperature and I give it a full throttle.. It is a great car and an answer is greatly appreciated.