Originally Posted by Rapid Dog
Just the opposite, smoother running meaning less jerkiness and more refined/controlled operation with both the throttle and the gearbox/clutch.
This doesn't mean a loss of torque.
2 of the best mods for a modern boxer are the cat removal and a fuel nanny or Accelerator (booster plug) module.
I don't see how removing the cat won't also reduce backpressure, especially at lower revs - perhaps the flapper valve can provide enough? I find it unlikely that you'll markedly improve performance at one end of the rev range without altering it elsewhere. Maybe the motor is just that restricted - but if you're optimizing engine air flow at one rate, it can't remain optimized at the lower rate, too, can it?
I wouldn't do any more than a slip on, and then only for sound - Illegal in my current state anyway, but do the premade cat removal systems include provisions for keeping the flapper valve?
(IMHO, the flapper serves two functions - readability and less obnoxious sound at low revs/around town).
Also, regarding performance, how in the hell is a 2011+ R12 not quick enough for legal speeds?
Then again, maybe the R12 has enough whoopass that losing some low end won't matter - I almost never go WOT as it is.