The only bolt on would be a stock early sportage stainless header. With a little work on the collector, they don't look to be too bad. If you replace with a miata header, some grinding is in order but I have talked with a guy that has done this and he said he noticed the difference immediately. Only thing is, you may have to have a bung welded in after your second cat in order for your computer to see that the cat is working.
Keep us posted if it is what you decide to do. Take and post pics of the process.
Everet <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />