I have a 987 CC R100R twin opposed BMW bike in So Cal. I need a ride if I fly there.
On the dealers advice, I put a K &N air filter
and Trapp exhaust on it after my first svc..
I was going to double plug it, like a real engine `till I learned the cost.
My paper work is 2,000 miles away with the bike. But the dyno said that I gained a lot of HP, not that you can`t kill yourself with stock, and the mileage went from 50 to 65.
The throttle return spring was a pain and removed. But you need to take care. A twist of the wrist gets a result. It is much less forgiving than a hog.
I have scared myself on that bike.
I`m riding a 400 CC one lunger around the farm. It has a lot of low end torque. I expect to dump it any day.