Take this info for what it's worth. I also have an 03 with a random misfire. Took it to a local tuner and he said that because I had a lightened flywheel, it causes the random misfire.

I also changed plugs and coil packs with no luck.

 

^^^ lol,i heard of something like that before bunch of horse crap

 

I'd close the gap on those plugs a little bit with your mods, depending on how much boost. Maybe run a dif. plug altogether.

 

iridiums are garbage. copper plugs, and differnt gap

 

P0300 is something totally different than Cyl 4 misfire which is P0304.

Do a compression test.

 

ya throw those plugs out

 

Most likely the gap of the plug. You can test coils too, but if youre asking how to do that you probably dont know how to use an ohmmeter. There are two coil windings in a coil, that have very high resistance between them. You must first test the resistance between the positive terminal and the negative terminal (<3Ohms). Second you must measure the resistence between the primary terminal and the secondary coil tower. should be between 6000 ohms to 30000Ohms

 

ams said that the twin disk will throw a code because of the chatter, but the exedy shouldnt do it unless it chatters alot. i have a quartermaster and it used to throw codes and it drove me nuts. i went with a standalone and that took care of the problem.

 

Theres really not enough info to properly diagnose the problem. Your tuner needs to datalog the car and find out whats going on when the misfire occurs. Most of the time a misfire code is the result of a bad plug, gap, wire, or coil. We don't know how much boost your running or how good the tune is, air fuels, etc. I would definitely at least change your plugs back to the ngk copper as mentioned earlier. Make sure your tune isn't so rich that its fouling the spark plugs out, those flames you mentioned could be related to an overly rich condition. Good luck.