Advice on Y-pipe
Y (stock location, 3"). The RT cats have about half
the backpressure of stockers by my measurements.
The Y means little, relative to the cats. This is a
fairly pricey way to go, retail, but can be found used.
This is my setup-to-be, still decorating my living room.
Two, an offroad Y which you swap back off annually
for a couple of days. These go pretty cheap, like I
think I've seen 'em at or under a hundred bucks. The
cats are the expensive item, and there ain't none here.
You would need O2 sims or programming, sims are also
out there cheap as more people pick up tuning sftwr.
Decent fab pics here: http://community.webshots.com/album/70033608PfFoio
Where you will get the most variation is the collector. If you bring your muffler shop the magnaflow $40 collector and have them build it with high-flow cats, nothing is going to flow better, relatively speaking.

