Join Date: Jun 2011
Location: San Antonio
Motorcycle: (Current) L5 750, L4 750, L3 600, (Past) L5 1000, K7 1000
Re: gsxr m4 pipe volume
Cheapest exhaust option is usually to get a used OEM muffler. Even if it's got some rash on it, who cares? You only need it to pass inspection, then swap back. Not sure what the prices are down there, but in the US your can get a used factory can for $20-$50 if you don't care what it look like.
If it's a full system you have to swap, OEM is probably still cheapest. You can get a used full factory exhaust here for under $150USD pretty easily.