Is CMI the only company to buy an exhaust system from, for big power
Like 800hp and higher?

Stainless marine gen III, make more power than headers and won't leak. 5 year warranty n their setup.....

http://www.stainlessmarine.com/?wpsc...and-5-ss-pipes

http://www.cpperformance.com/p-13433...collector.aspx

What's their warranty?

I don't know , just answering the original question . Some research is left up to the buyer .

Someone else said Stainless Marine to me too, how come you don't see them on the Merc 850 1075's or the bigger engines in general?

I'd think the major reason is that all the new high HP merc stuff comes with CMI and people don't know any different, so when it comes time to replace, they pick the phone up and call CMI. Second reason is they're not as pretty as polished headers. When you weigh the pros and cons it's a no brainier.

Pros: no leaks, longer warranty, make more power, cost less than CMI

Cons: don't look as nice

Do they really make more power over true long tube headers, I'm not knocking you because I'm sold on them. I've just never seen it proven that they out perform headers. I'm ordering two sets to replace some leaky cmi's I have now but was willing to accept a slight performance loss for longevity

Make more power ? I have seen no proof of this other than maybe the Keith Eikert exhaust . There has got to be a reason you don't see SM and similar on big horsepower engines . Someone correct me if i'm wrong .

stainless marine will make more power on blower motors than any tubed header than are larger and flow better. The blower pushes the exhaust out. On N/A motors the stainless header makes a little less power than a tubed header, not a large difference. Have owned both and dynode. I was much happier with Stainless Manifolds