BMW Questions? Ask a BMW Repair Expert for Answers.
Depends on many factors.
How much money do you have to spend?
How much power do you want?
How long does the engine, transmission and rear axle need to last?
With the engine in standard form, the compression ratio is already fairly high, so it would only take about 5psi of boost safely.
7-10 psi would be possible with more tuning and water/methanol injection.
As you may be learning, for each 20hp, the price goes up exponentially.
If you find a shop in your area that can do this sort of job, I would say that would be possible.
For 330 hp, it would be forged pistons at 7.5 :1 or so, ported cylinder head, full engine balance, fuel system upgrade, ecm dyno tune etc.
I would worry about if the transmission would be up to the task.
I'm not trying to spend your money here, so if you like a Mustang, then you can get WAY more power per dollar out of it.
If the BMW is in good condition, why not keep it stock, and get another car to hot up.
Hope this helps.
I hope my advice has been of assistance to you.