E30 Zone

My recently purchased 1990 325i has a standard exhaust, and unusually a cat (factory ordered)

I'd like it to sound a little fruitier, but still look standard ish, and not sound like a boy racer

Any advice?

Thanks

Remove the cat., knock seven bells out of its insides, pour the debris out, and refit.
Will probably increase the noise level, and will definitely improve the MPG.

After removing the cat, disconnect the O2 sensor and check/adjust the mixture to 1.5 CO (as long as rest of the engine is working as it should be with correctly adjusted valve clearances)

If its a genuine BMW one in good condition I may be interested in it

Leave it alone. It's how BMW intended it to sound.