This is normally caused by KR. I had a few of those knock retards too, I always blamed it on something else. When I bought the tuner, finally found out that it was KR.
What did you do to remove the kr?
(sold) 1998 GP GT- ssm90'd. ported blower and lim, zzp fuel logs, l67 inj, 103's, zzp 2.5"dp, magnaflow mufflers, zzp plog, 3.8" ssm90 pulley, eibach springs, short db's
2002 Z28 LS1- stock for now
2012 chevy sonic 5spd