E30 best value performances options (after 23HP increase)?

[milpas421]

I bought my 1989 325i cabrio just last November and have been enjoying it immensely as an everyday driver. I’m a student and don’t have too much money to throw at it, but I have increased the performance with a chip (off ebay), K&N filter and Signature Motoring heat shield. All in all this stuff was less than $200.00 and gave me a whopping 23 HP/19ft/lb torque increase on the dyno. (The Signature Motoring performance intake was actually in first and gave 8.3HP increase and the chip did the rest; except the chip w/stock intake only have +11 HP instead of the 18-20 advertised). Either way I’m happy and the car feels a lot lighter and responsive.

My next step is a performance exhaust. I’ve got maybe $450 to spend. Can I get something decent for this? Does anyone have tried/true recommendation? If anyone has something for sale, I'm interested. I would need something street legal and bolt on that doesn’t require any custom welding jobs. Thanks!