Hey i have the RB street header, presilencer and stock or OEM muffler and dual pipe thing out of the pre. It looks to me that the stock pipes are the same diameter as the RB muffler's pipes out of the presilencer.
So what im thinking is that the RB system isnt gaining any horsepower through those dual pipes?
What i want to do is put on a Borla (because its not done by anyone i know of) or if i have to a Magnaflow, but if this rear section thats stock will rob horsepower (more than 2 or 3 hp that is) i should prob replace it.

Pardon my confusing post.

 

the heat from the exhaust may eat up a borla muffler. they split when they go bad. teh dual pipe syatem has been proven the most effective. i wouldnt go with the single pipe. the RB parts you have are top notch!

 

i just finished putting my exh. system on, i have a rb header and presilencer as well... i bought the pipes from rb na di got some can mufler off ebay. i noticed that the stock pipes were about the same size as my header and pipes, but went ahead and welded it all together two minner bends went under teh axle up and out, my butt dyno can deff. tell the diff! my mech secs. kick in soooo much harder now its great!.. stay with the rb setup its meant for the heat our cars put out.

 

wow i have no idea what you said there 83gsl.... *cough*grammer*cough*