Aftermarket exhaust modifications fall into two categories: full systems and slip-ons. The full systems replace the entire stock system including the CAT. High-end exhausts with titanium headers still offer fair weight savings compared to the stock ones. Some headers have various tapers and crossovers to enhance low- and midrange torque while still improving top-end power. In fact, some systems offer minimal gains in peak power, choosing to instead shape the power curve for more midrange and a broader horsepower peak.
However, one possible disadvantage of aftermarket systems is that they require the removal of the servo-controlled valves that some OE exhausts use for better low-end power. Although installation of a full system is a relatively easy modification, many riders choose to mount slip-on systems. These range from simply bolting a canister to the stock S-bend of the header or replac-ing the exhaust from a mid-point back.
Since the system becomes a hybrid of OE and aftermarket components, the power gains are mini-mized. Still, if your bike has a heavy muffler, shaving those few pounds can be the same as adding some horsepower. Also, slip-ons don't require the removal of exhaust control valves such as Yamaha's EXUP system.
SO... Is it all worth it? Do you get power gains with an after market system? I would suggest you do, infact having an after market full system and power commander mapped has given my R1 considerable power gains. I will be getting on the dyno this month and will document the results for RBB