I think you are asking that question on the wrong NG.

I don't get what the previous mail is on about  re mods to porkrers ,
however........I'm in the UK and here you can de-cat an exhaust if it is pre
1992 and I have.....it adds 12 odd hp and I got it from
http://www.promaxmotorsport.com/ who also supply a good upgrade chip or a
package inc chip , de-catpipe and K&N replacement filter.(the exhaust is
made by Janspeed and results are available at
http://www.essentialstyling.com/944_s2_system.htm )
It works well on my 91 S2 and has a deeper exhaust sound (not annoying or
stupid loud). The kit has been dyno'd on an S2 and put out 253HP ,
admittedly this will not be available on all cars but hey its all good....)
   I have tried an induction kit and it sounded like a MK 2 Ford Escort (a
v poor UK old car (aplogoies if you are into them)) with no air filter and I
cannot recommend one as it cheapens the marque.
Have fun

Paul944S2

Jim

I have a Bursch (sp?) on my 87 na and it has quite a rasp once you get some
rev's on.
I think I saw them available through Performance Products.  They're no
cheap-- if memory serves somewhere in the $600 bracket.  Many years ago I
had one on a 914 and it had a similar aggressive sound.  One thing--- it may
attract the local constabulary and that may not be a good thing.  Good luck