I love the side exhaust, but also love the tips of my Borla's sticking out the back....tough choice IMO. On the HP - when I ordered my Borla from Borla directly (had a 50% off from a track event), I asked about it they said it was minimal with the side exhaust just a bit more restrictive (I bet I wouldn't be able to tell a diff though...)
I think spintech makes some. I have some dynomax bullets on order that i am going to move forward to the h-pipe, with a 90* bend out to the side with some *gag* chevy style tips
i have the dynomax super turbo mufflers for my side exhaust. its a different sound, but its awesome. it have more of a deep rich sound to it. also i got them fairly cheep. as far as the hp loss, i could tell a difference, but its worth it!
Here is a relatively inexpensive way to get side exhaust and clear subframe setups. It also more than likely flows a little bit better than some of the 180 degree mufflers like those used by Borla Bassani and dynomax.
All you need are some flow tubes, a pair of mufflers and 4 mandrel bend J bends that you can get almost anywhere. I did not come up with this setup I just borrowed the design and put it to good use.
The above pic was my blueprint.
This is my setup. Note I used center outlet muffs for more room.
This setup may not be for everyone but it is very functional. It's just not flashy like some of the other kits out there. lol my car is not built for looks though.
I had a Bassani side exhast on my 94 Cobra. It looked better than if performed.