Unfortunately, I don't keep up on what upgrades are available for the 60 degree engines (3100, 3400, 3500, 3900, etc). I swapped out my 3100 for a 90 degree engine (3800) back in the mid 00s due to lack after aftermarket and never really looked back.

As far as I know, there are no headers available off the shelf. Obviously a good custom/performance shop could build them with no problem, but customer headers would be crazy expensive for the power gains. Competition in the header market is what helped get 3800 headers down to reasonable prices.

As for a downpipe, it depends what you want to do. If you're ok leaving a cat in it, any exhaust shop with a mandrel bender can make one. If you're set on deleting the cat, you're going to have a hard time. Best you could hope for is to have them build you a bolt in catless downpipe and then you bolt it in yourself at home. There may be shelf stock downpipes by now though, I'm just not that familiar with them.

 

This may be a silly question, but I do believe the answer is yes, but I wish to confirm, this car is fuel injected, yes? I was reading more about mufflers and deleting them completely and all that and read a fuel injected car relies on the back pressure created for the engine from that zig zag pipe and actually modifying the pipe, say into a straight pipe like I was hoping to do, it gives you less power or makes you weaker. Can anyone confirm this?

 

Yes the cars are fuel injected, yes removing back pressure is bad, but doing simple muffler modifications will not make a difference on the back pressure.

If you got headers custom made, and the primaries were way too large, then you would be worrying about back pressure, from anything from the cat-back, you are fine

 

It is fuel injected as chibi said. More specifically, it is port fuel injected (not to be confused with throttle body fuel injection or direct cylinder fuel injection).

As for a muffler swap losing power, I wouldnt worry about that at all. The impact of a muffler change on performance (positive or negative) is virtually nothing, so just do whatever setup sounds best to you. If you think about the system as a whole, there are a lot of other things restrict the flow - the stock exhaust manifolds, catalytic converter, resonator, numerous bends to route down the firewall and around suspension components, and also 15 feet of pipe. You'll certainly reduce back pressure in the system by straight piping the muffler, but it is only one component of many in the equation.

A real world example of how little it matters is on my gp gxp. Its a little bigger engine, but it's the same principle (NA engine). I installed a y pipe and an electronic cutout in place of the resonator, just after the catalytic converter. This allows some of the exhaust to completely bypass the entire exhaust system after the cat, reducing back pressure far more than a straight piped muffler would. The end result is that open or closed, the car runs the same ET in the 1/4 (traction limited obviously), and I averaged about a 1 mph gain the 1/4 trap speed - which is virtually nothing. I only did it because I wanted it loud, but my wife wanted it quiet when she drove it, so it was the best of both worlds.

 

i have fake dual, sounds like crap....but i bought the car this way

 

I would like to put true dual exhaust on my Jr model that has the 3800 Supercharged what do you guys think. And where can I buy headers and the rest of it for the 2004 monte

 

Cant really go true dual on these 6th gens.. Unless youre prepared to do quite a bit of custom work.. Honestly if you have any metal fab skills you could get it done but its really not worth it..

Speed daddy and DNA motoring Have direct fit headers with 3" downpipe and those are the cheapest youll find.. Just over 200 for the whole kit..