Y Not Long Tubes?
 

OK, they're not exactly emissions legal but long tubes will dominate over shorties. If you have to pass the sniffer then have a set of cats welded on your h-pipe. It's not uncommon to see long tubes give up to 0.5 sec and 5 mph gain.

I know this is the minority opinion, but hey, just some food for thought. If you ever think you'll install long tubes, might as well skip a step and do it now. :)