Is there any advantage to be gained by installing just risers vs headers and risers? I an concerned about the costs (have twins) and the install itself (once again, twins). I have read where the Mag HO stock manifolds flow pretty well.

well the new CMI headers produce 60 HP i think...the nice thing about the stock exhaust is that it is a dry-joint exhaust system, water doesn't get in the engine...nice if you are running in salt water...

The new manifold and riser design on the 496 is a world of improvement over the old design on the 502 and 454. The CMI headers for the 496 are bad to the bone. You should consider those. I would love to have a pair on my HO's that's for sure. There is one big problem though.....they are not compatible with Captains Call.

Tried changing from the factory cast iron risers years back to a set made by a company called FastGlas,,,looked cool, easier to work around most difinitely lighter,,,,,and absolutely no performance gains.Also had water flow problems at higher rpms.
Personally don't think it would benefit you,,unless your risers are bad...Save your money and buy the CMI's.

I'd agree with Slick02 it's all or nothing for any gain. I would think that without the complete package the flow will be restricted. By the way on the HO are the mainfolds cast or aluminum?? Those cast mainfolds with risers are believe are about 150lbs a side.

Thanks for the advice. Along these same lines, has anyone removed the turbolator plates on their Mag HO? Is it worth the effort?