Just in case anyone is still interested in my N21R trials and tribulations.

I tried the 9901 + 41030 and 41021 (sorry, won't buy 005 header...) again this weekend, to no avail. The mill simply refuses to rev properly, and is a low-rpm dog, no matter how hard and what I try. When cranking out max HP (ie not much) it will easily temp 270F on my newly received exergen (hurray!) and keep climbing, if I richen it it just sounds wrong and is a turd in the straight. There is no way any different header could add that much low- or hi-rpm HP, so I will simply conclude that 9901+N21R is anything but the hot ticket at least on my mill.

During the same practice session, I also swapped pipes in 3mn back to the "standard" 086HS, using same fuel, same plug, same filter, same weather, same clutch, just swapping exhausts - this is litterally night and day, suddenly the engine lives, is stable, not overheating, not stalling, it's nice nice nice, a real $135 treat

what, again, is stunning me is that my buddy's N21BF is a screamer with 9901+41030 so either NR's QA has some serious slack in their process, or there is more changes from the N21BF to N21R than sees the eye...

I'm done with testing now Overall I'm happy with the 086HS, so it's now and forever my N21R's official exhaust. Screw runtime, I'd rather have the car drive like it should than -maybe- get 10mn+ refills and not be able to clear the jumps...

N21R + 086HS = Nice little <$200 combo

Paul