i have a 96 tacoma 2wd extended cab 4cylinder 5 speed that is making a high pitched ticking noise when the thottle is released around mid to three quarter throttle. i step back on the throttle and it goes away. doesn't do it at low or high rpm though. i though maybe wrist pin but figured that would be noticeable at a lower rpm also. the truck has 364,000 mi. and i have owned it since 102,000. oil is changed at 3000 mi. i run castrol gtx 20/50. any ideas?