it sounds like something its loose when i step on the gas after 4500 rpms but if i go easy on it it can go to red line with no noise at all. i check everything but i cant seen to find the problem. the engine its a y8block z6crank pm7pistons and rods d15b vtec head p28ecu never tune. was runing perfec for about 6 months. has any body had this problem before?