E30 Zone

Hello, bought my 1st ever 325i last week and im over the moon with it compared to my old 318is's.
Purchased from a middle aged bloke, genuine 66k miles etc,

He told me it had a super chip in it and also handed me the original spare one.
Only problem is.. Once i take it to 6k revs.. it jolts and the needle bounces back to roughly 4k revs (instead of bouncing off the limiter) sometimes even back fires and a large flame comes out the exhaust pipe!

Any ideas etc, try a different standard ecu in it?
TIA

I'd swap it out for a speedtouch Wild chip, £30 and by far a lot better than anything else.

Needs to be a facelift model with the later Mtronic injection though

yes mines a h reg 1991,

replace with the standard chip but don't thrash it straight away it needs to idle for ten minutes and be driven at varying loads for an hour before you start taking it to 6k

thanks pnd