I have a 92 Toyota truck with the 3vze. I was getting code 21 and 52 and discovered a HG leak. After new head gaskets still have code 21 and 52. I have already checked wire going to ECM and has a new pigtail I just don't want to put a $130 KS in if its not bad but truck runs like ˟˟˟˟ no power

 

Does code 21 have anything to do with head gaskets? (Hint: no.) You might want to fix that first; it's usually not too difficult, and you'd hate for it to be masking other problems.

How did you "check[ed] wire going to ECM"? The pigtail is the most likely to fail (and the Knock sensor itself not too likely), so the wiring end-to-end is where I would look next. Make sure you have continuity from the ECM to the sensor, and make sure the shield is adequately grounded (remember: it's grounded only at the ECM, not at the block or anywhere else.)