i just got a 91 GTR. it runs smoothly until it hits 4000rpm @ full throttle. i cant get past 4000 rpm cause it jolts heavily. i revved it to 6000rpm and it seemed fine. im thinking its my sparkplugs but im not sure cause u can rev it past 4000 without problems. sorry for being a n00bcake but pls give me some ideas and solutions. i heard rumors that old rb26 engines has an oiling problem @ high rpms. is it caused by this oiling problem?