Just got my first skyline(r33 gtst s2) the other month and was impressed with the performance and overall car, i got it 100% stock so i put in a KN pannel filter next i got some yellow jacket coils and new spark plugs( NGK iridiumi BKR6EIX-11) car was running fine then i fit the plugs and coils and car was running rough as and would misfire after 4000RPM so i thought it might be the coils i put the old ones back in and it was fine at idel but still missfires at 4000rpm.
Can someone help a newbie out?
Thanks