Strange Rev limit and exhaust pops!

This may help someone in the future. My S1 VHPD developed pops and bangs on the overrun, felt slower than usual, felt like it had a misfire and sometimes had 5000ish rpm limit.

After some detective work it appears the problem is the vehicle speed sensor that feeds into the ecu, not the Stack dash. I guess it uses it to control stationary engine idle speed and gets confused with intermittent signals and probably messes up the IACV. I just cleaned the connector and all now appears to be well, running smoothly again.

My clue to the problem was I had always noticed the moving idle rpm is about 1600 and it drops to about 1200 when the car stops moving.

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