I read on one of the chat sessions with the SRT team:

Question: There have been quite a few controversial posts on different forums lately concerning aftermarket headers for the 6.1 engine. There have been claims of increases in the range of 20-30hp. What would you guys say is the max possible attainable HP, if anything, with aftermarket headers vs the stock headers? My contention is that there really is no room for improvement in replacing stock headers alone. But the argument is that the factory had to take cost considerations into play and therefore may have left some HP on the table.


Answer: That sounds extremely unlikely. The stock headers did not leave much room for gains in HP. We would put it more likely in the realm of 2 - 5 hp.

 

ive never taken a good enough look at them to know for sure, but lately so many performance cars are coming with an exhaust manifold so near the shape and flow pattern of a "header", that gains would be minimal...however, when you take into effect things like inside and outside powder coating, increased size, etc...it would make a bigger difference.

also, if the exhaust manifolds are similar to a "shorty" header, where the exhaust system comes up into the engine bay to meet them, then the exhaust travels through the "y-pipe"...you can often see some gains in going to a long tube header, which extends down under the vehicle, then into a collector.

 

From what I have been reading with the 05+ mustangs, replacing the shorties, doesn't give you much HP's that is worth the money. LT's I have read give around 30 HP's. But the problem with the LT's is that there are not street legal because of smog laws. This even goes for catback exhaust. I remember when that mod would give a decent output, but now, it may gain 1hp. Basically people just get the axleback and is more for the sound than anything.

 

i should point out that on cars not really intended for performance, a shorty header and catback system can make a much bigger difference...non-performance vehicles have very little R&D effort put into the design of the header and exhaust system, but with performance cars, the R&D people are focusing on getting the most power with the least amount of emissions or heat issues...
techman, there are NO LTs that will pass cali smog?

 

From what I have read, it will pass tailpipe test and ecu test, but if the tech were to visually see it, he could fail it because it isn't smog legal. Then you would have to put the old one back on and goto a CA smog station for inspection.

Also if the police see it, that is a ticket and you would have to take it off and put the other back on then take it in to get it signed off.

 

i would hate living in cali, just based on that...

 

Every place has their pros and cons. Depends all on what you like to do. My big thing is Motorcycles. I like the fact I can ride all year round here. I did the east coast thing, and that wasn't for me. I wouldn't mind living in a different area than L.A. though, but the wife's job prevents that.

 

if i had a bike, i would see your point a great deal more, but i dont like people telling me what i can and cannot do to my vehicles, and i thought that PA was bad, but cali takes it to an extreme. whats funny, is that the mirada is not legal in PA because it doesnt have cats, but it runs MUCH cleaner than my old ramcharger...

 

Blame the Eviironmental wackos, and the politicians who don't know sh&^ who just look at papers the wackos give them and say OK, sounds good to me. and sign off on it without proper research.

You can always get a 74 or older, it may be 76 now. They are smog exempt.

 

Okay, so all that being said, what would be the the top changes for performance enhancements on the 2008 Challenger within a $2K budget and destroying the warranty.