(E30) Knocking with a Jim C Chip

["Robert Tobin" <RTobin@xxxxxxx>]

I recently upgraded my car with a Jim C chip from Turner Motor sport.  The
drivability is definitely improved, but I'm getting some knocking under hard
acceleration ( i.e. from 3rd gear at 3,000rpm, and step on it 3/4 pedal to
4,000).

My first tankfulls have been Amoco Ultimate, and then Mobil 93 octane, which
improves things a bit.  The car has 78,000 miles and was tuned at approx
50,000.  By the way, it's an '88 325iS and the car is otherwise stock.

My concern is heightened because I'm planning to do the NYBMWCCA autocross
school on the 30th, and I expect to drive it hard.

Short of adding an octane boost, is there anything I should look for as a
fix (fuel filter, air filter)?  Do any of you have luck with a particular
brand of gasoline?

Thanks very much
Rob Tobin
BMWCCA #148884

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