I have a 1999 v10 with 66,000 miles, heres what we have tries so far, new spark plugs, fuel filter, checked all coil packs, cleaned mas aif flow sensor, still misfiring though, there are no codes and the engine light is not on, you really feel the mis when going up hill at about 4o mph and at idle. Any input would be great.

 

I am not an expert, but check your fuel pressure and see if it jumps around. How often does it missfire, ie. every two seconds or just random. If it is constant then I would look at fuel. You may also check the plug wires for cracks or wear. If you short a wire the plug wont spark. Good luck and post results.

 

It seems to be random which makes it even harder to track down, I will try the fuel pressure test tomorrow, thanks for the suggestion.