All of a sudden I got this weird knock retard at 2200 rpm. While cruising on the highway at 2200 rpm 75 mph under VERY light throttle I get knock counts that look like this 02 , 04 ,07 ,11 ,16 24 ,29 ,35 ,39 ,41 on teh scanner until the car starts making weird noise and bucking and it keeps retarding even if I let off the gas. It'll stop after a while or if I put more load on the car and give it some more throttle it'll go to 0. below 70 no retard over 75 no retard. It does this intermitently . I have tried an ESC Module out of a 4.3 S-10 that I got at the junkyard and it doesnt do it now. With the junk yard ESC the car runs great. so far knock on wood. No codes are being thrown. Its an 89 350 TPI