is the Dual Cat option on TPI cars worth more HP that a 3" system?

i converted my 5.0 TBI to 350 TPI and went with a 3" system from the header collector all the way back. i heard the dual Cat gives 20 hp more than a full 3" system. is this true?

also did all 350 TPI's have the dual cats in 92? im trying to stay smog legal here in CA

 

You just opened a can of worms! Well, what the heck. You might want to do a search because this comes up all the time.

Now, here's what's going to happen. Somebody's going to pull out their calculator and say, yes 2 2.5" tubes are better than one 3" because... yada yada yada. And then somebody else is going to... well, I think you get the idea how it goes.

Why don't you ask DynoDon what he thinks? Or, maybe he'll just read this and answer it on his own.

 

well i was more concerned about being smog legal. if all 92 350 TPI's came with a dual cat or not. i dont want to get busted by the smog police when the time comes up in Feb.

the added HP(if any) is just a plus

 

Ok, here's the deal.....our cars came with TPI (f-bodies) so it doesn't matter if you change from TBI or carb it will pass without going to a referee. Some also came with dual cats, so same thing applys, if challenged just say it's a '92 motor even if it is an '88 car because you can change to a later engine with no problems.
They didn't come with G92 until '89 (dual cat part). Besides most don't know the difference.

 

awesome,

still need to get a new cat since this one is wasted. hey Don i have an idea on the cold start to my car. i'll send you a PM about it

 

A really **** inspektor can determine that in '92 (and since your chassis is a '92, you have to meet at least that standard), a single-cat car would have a 2-1/4" cat, and a dual-cat car would have two 2-1/4" cats. If you have a single 3" cat on there, it could be grounds for rejection, because the factory didn't put a single 3" cat on our cars in the 1992 model year.