I had the heads rebuilt last year, but i do not think they replaced the springs. Seems like like before if i had knock it was in 3rd at wot.O2s 780 Will week springs cause it to knock sooner? I installed the te 61 turbo and i had 13.7 knock with the injectors at max and Alky at max. so i took it off and went back to the Ta 49 turbo. Thanks for the help.