how restrictring are the sidepipes??????

this has been debated alot on this and other sites. Basically it comes down to the fact that you most likely not make any gains from going to the side exhaust and maybe even loose a few HP but not a lot. you can go into the specifics as much as you want.

Is there a specific reason that you are going with the side exhaust? I know that I am cause I like it and I plan on getting the Steeda 5-link rear suspension and that suspension does not allow for rear exhaust on a solid axle..
 
The pipes are going to do two 180 deg bends. I can't tell you much it will hurt - could even be unmeasurable vs a stock exhaust - but it WILL hurt. The only reason to do sidepipes is for looks. If that is what you are after, then go for it.
 
i have the borla side exhaust on my 98 cobra. from what i hear this is one of the few side pipe kits that don't hurt your hp. they don't help it, but they don't hurt much. they do look and sound great. the 180 bend is in the muffler. as far as other kits go i'm not sure. the only problem that i have is trying to put the car up on to a lift. the pipes and side skirts are in the way. other than that i love mine.