Do you have to have anything done to your computer because of a lean condition when using the stainless marine exhaust ??

Not on the regular ones. I'n not sure on the Gen 3's.

I'm running them on my 1997 502MPI without computer mods.

I'm also running them on my '96 502 MPI's without any computer mods as well. Nice product & good support from factory. Not the cheapest manifolds, but best bang for the buck.

How do you tell which manifolds you have?

The threes have individual runners all the way through the manifold and extending into the collector, you can see it on their web site. The high torques (earlier), only have the runners part way up the manifold. I had to get these because I needed to twist the collector pipe to a side outlet.