1993, twin turbo, automatic. Modifications: Pettit cold air induction, down pipe (pre-cat eliminated), air pump eliminator kit. I want to replace the catalytic converter with a new center section. I don't want the exhaust to be any louder and I want to avoid any drone effect (that a straight pipe may cause). I'm looking for advice on what to buy. Thanks

 

Rx-7 store magnaflow midpipe, but it will probably be a bit louder than your cat (i think anything will be louder)

http://www.rx7store.net/product_p/resmidpipefd3s.htm

 

^^That is one good choice, I run it and it is not too much louder than stock. BUT like mentioned above most everything is going to be louder than the stock cat. You may also really consider another type of cat conv.

Honestly, if there is nothing wrong with the cat, then just leave it be. It is not hurting anything by being there.

Also remember when you free up the exhaust you have to mind the boost levels your car is seeing. By decreasing that restriction you will NEED some way to help control the boost. Also, if you have not already to need to get a boost gauge installed so that you may monitor this. Particularly if you are still running the factory ecu and plan on decreasing the exhaust restrictions. By doing this many individuals have lost engines very quickly, so be warned.

 

rx7.com get the bonez cat it workes great and holds up to the heat. I pass california smog no problem with mine.

 

Noticed in Jeff's reply about his 4.33 differential modification. I did the same! incredible acceleration difference, right? However, I could not find where to get the proper speedometer gear for that ratio. So, I'm making do with a conversion chart.