Actually you may lose a few ft.lbs of torque between an exhaust and y-pipe. The diameter of the Borla/Bassani is 2.25" vs stock 2", therefore you get less backpressure at the cost of 2-3 ft.lbs of torque. Of course you make up for that loss in you horsepower figures.
I went from just a KKM, and added my Bassani and gained ~5hp. but lost ~3 ft.lbs of torque. When I put my Y-pipe on (SHO Shop Off-road) I gained ~2 ft.lbs back, and gained about 3.5 hp.
Click
here to see my last dyno plot.
I also had to add a resonator after I went with the off-road pipe, there was too much drone and it got raspy in the upper RPMs. So all in all it cost me about $200 for the extra 3.5 hp, not including installation and reapir after the flex joint broke.
Hope that helps some.
