Keep in mind all the things you need to do to:
- possible upgraded clutch and new guibo
- ensure that every bushing is in good condition
- brake (hardlines, softlines, rotors, pads) are adequate for the upped HP
In TCD's case, I think you need a complete exhaust system from the DP back.
Doubling the WHP on an E30 is stupid fun, but it sure can get expensive. For the OP who didn't want to invest $150 in a cheap welder, honestly buying a faster car would be cheaper.
Get a beat up E39 540i for $5K and kick the Honda kids asses.