[Vettezuki]

I have a H&C LSx making about 390 WHP. Defiitely has some back pressure probably from the now tired OE cats. I'd love to go to LT headers, but living in CA means that ain't legal. There are Legal shorties and now Magnaflow has a new (not quite out yet) OE replacement Cats that I can use. While the flow from the shorties probably isn't all that much better than the stock manifolds, I figure ceramic coated shorties should still do a much better job than the stock cast iron manifolds at getting heat away from the heads.

[94cobra69ss396]

Shorty headers will be a good improvement over the stock manifolds. I don't think they will be quite as good as long tubes but they are at least legal. You also need to improve the rest of the exhaust.

[BRUTAL64]

You are on the right track