Was the injector not opening sometimes? At an idle, you can place a long shafted screwdriver up to the injector and your ear (blade to the injector, handle to your ear!) and definitely hear if it is not opening regularly.

no, no separate diagnosis fee. Total cost BTW was 2 hours @ $90 + the $179 injector part, for a total of $359 (they threw in the taxes). From what my regular mechanic said, the shop probably didn't change the coil, they probably just swapped coils because nothing looked like it was new. Normal practice from what I understand.

I misuderstood you, I thought you meant that the total bill was $179. $179 for just the injector and then two hours on top. Too much in my opinion.

If he had gone to the dealer the bill would have been well over $600. He also got a loaner car. The correct book time @ $90/ hr + $179 = $404+tax. I think he was charged fairly.