Recently I was driving my G, fairly hard when having the car floored in 3rd (2003 coupe 6mt) the car started shaking violently and was surging. It felt like the car was gonna just die, so I pulled over in a parking lot left the car for about 2 hours I came back started it again and the idle was going crazy, was around 1800 RPM just spewing out smoke out the exhaust. When the car warmed up it seemed straighten out the idle slightly was still high but not nearly as bad and I attempted to drive the car home which was a very tense drive since the car was surging the whole way luckily I didn't far to go all the while throwing a CEL. So I disconnected the battery overnight hoping resetting the ECU may have helped. Next day start the car idle still not normal but much better proceeded to drive the car everything seemed normal about 15 minutes after CEL comes back on back to surging. Did ECU reset, put in some fuel system cleaner left the car alone another day. Next seemed to be running fine, got a hold of a diagnostic tool and found the code p-300 random misfire(which is completely useless) after driving with the DT hooked up to the car it finally gave me a P-306 cylinder 6 misfire.

I drove the car for about a month with no issues only a minor one where on a steep hill in high gear at low rpm flooring the car caused it to misfire and shudder. As soon as I got to even ground the car was completely fine again. So I finally replaced the plug and coil pack on cylinder 6 (plug gap was way out somehow) have been driving the car no issues with the DT hooked up no error codes. However I did notice once on a slight incline in 6th gear at about 1000 RPM and flooring the car it did misfire but no CEL or error codes through the DT. Is it possible that in that situation floor the car when the revs are very low and load is high it's dumping in a ton of gas, while the engine is not able to draw in enough air? shot in the dark I guess

 

If you floor it on flat road it never misfires? Might be the injector or the air filter needs replacing