2001 Acura CL Engine Misfires

I'm trying to figure out what is really wrong with my sons car.

The first mechanic thought it was the computer so he took it out and replaced it with another one. The problem remained so he put the original back in. Recommended we go to an Acura dealer for a diagnosis. Here are their results.

CODE PO 300-306 ALL CYLINDERS MISFIRING. DIAGNO SED VEH AND SWAPPED COILS WITH KNOWN GOOD COILS AND MISFIRE WENT AWAY EXCEPT WHEN VEH STARTED COLD. RECOMMEND REPLACE ALL COILS AND PERFORM VALVE ADJUSTMENT.

CODE 01-1 POEN CIRCUIT IN DRIVER AIR BAG, WOULD NEED NEW HARNESS TO START.

2 issues 1) engine 2) airbag

The airbag light has always been an on off issue since he bought it used.

The dealer said it is a wiring problem to the airbag not the bag itself.

I don't know if it is related but the first mechanic tried to swap the air filter with a Honda and it didn't fit so he put the original back on. The original that came with the used car is not the one that would have came with it new. The other owner put on a cold air intake for better performance. The mechanic was trying to put on the Honda filter so that the car would pass smog. A week later the car started having engine problems.

He has had the car for about a year.
Any Ideas?

Thanks