Five years ago I found a NOS TRD supercharger at an East Coast Toyota dealership and had my local dealership install it on my 1997 80 series. For the first 3 years I battled low octane California “premium“ fuel engine knock at low rpm high gear loading. After replacing stock plug wires and installing iridium racing plugs, the knock improved. That was going great for a year but now it’s been a year of chasing an intermittent, unpredictable low idle (200 rpm) that I cannot reproduce for the mechanic. Three times however the condition has thrown a 0401 code (insufficient egr flow) and the modulator, vsv valve have been replaced. The error code resets but has returned. We’ve replaced the air/idle control valve and traced all emissions and vacuum lines verifying against the factory and Magnuson diagrams. The MAF and throttle body have been cleaned and fuel pressure has been verified. Vacuum readings are within normal. Fuel economy is normal and performance is great when driving but coming up to a stop, I just don’t know if it’s going to sputter or flat out stall. If I have to hit the starter, 9 times out of 10 it returns to a solid 650 rpm idle. I’m fully expecting another code any day now so any feedback would be appreciated.