Code 302, engine misses on startup for 10 or 15 seconds, then runs fine.

Question

This problem only occurs for several seconds on start up. Occasionally it fires up and runs perfect immediately. Sometimes it will run for a week or more before check engine light comes on, even though it's obvious that it misses on start up. Problem is not confined to engine being cold. Often after sitting for only 10 minutes, it misses on start up.
The basics have all been replaced. Rotor, dist. cap, plugs, plug wires, injectors, fuel filter, IAC cleaned, throttle body cleaned. Compression tested 157 to 160 for all cylinders.
Coil has not been changed, but it has a discreet coil, used for all cylinders.
Mechanic is stumped!

Answer 1

P0302 Misfire number 2 cylinder

You may want to inspect the fuel pressure regulator for fuel leakage, if fuel leakage occured at the fuel pressure regulator vacuum port it would go into the intake manifold just right where the number 2 cylinder is at.

 To check the fuel pressure regulator with the engine running pull its vacuum port out if fuel is seen comming out the regulator would require replacement