My suggestion if your on a budget you can get a M20B25 for relatively cheap with the harness and ECU and transmission if you so chose. But if you want to save and get some real power in that get a 24v swap like a M5X/S5X.

The M20B25 is a relatively easy swap, and you get 140 hp not a massive amount but its better than a broken car.

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The E30 is the single greatest BMW in my mind.