Have you rewired the knock sensor with GOOD shielded wire? There's a writeup on it which is commonly linked to here or you can find it via Google. A code 52 doesn't mean the car will be in permanent limp mode, just that the ECU is detecting a significant failure in the knock detection system. If the code keeps coming back, don't ignore it.
Depending on your goals you may want to just look for a good, used Lexus AFM and use the electronics from that in your KVAFM's housing. The electronics are the same it's the housings that are different. This will have you up and running a lot quicker and for less cash. I like the MAFT Pro, but if you're not out to upgrade to S/D or can't find a Lex AFM either the MAF T or MAFT Gen II will be a simpler install and setup.
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