[pmanaz1973]

I've been running the EFI Classic Silencer fro our host on my 2014 C5 with a factory air filter and have not had any issues at all.  Bike feels a bit better and the silencer is not loud, but has a nice muted thump and is lighter than the factory telephone pole for sure. 

[gremlin]

I have a efi bullet, and have recently replaced the exhaust with a louder one following an incident where someone almost knocked me off my bike because they "didn't see me" however my plug is fouling up more since replacing the exhaust. Now I know that the ECU wont learn the new exhaust and there's no way in hell I can afford (or want) a Power Commander, does anyone have any idea which way I should go temp wise with a new plugs.

Many thanks in advance.

Before you end up chasing your tail ....  consider this:

*IF* your exhaust gasket (at the head to pipe junction) is mis-aligned and leaking.

*THEN* in between exhaust pulses, the negative pressure will draw fresh air into the pipe.

This influx of fresh air will affect the O2 sensor reading, and your injection controller will enrichen the mixture to compensate.

Sorry...  no *ELSE* in this script.

[gashousegorilla]

  A good seal and getting the angle right on that head pipe HAS been a common problem.....

  No empirical data or anything?    But I DO know that this one came out of a header where the fibrous washer had long since blown  away.  I think the person  who is looking for help and started this thread. Should maybe check his o2 sensor, before that new plug may start looking the same way...  Just my humble opinion. 

[Sectorsteve]

+1 for the comments on a potential leaking header pipe, or general leaks anywhere.
Ive had exhaust off more than i care to mention so mostly when the bikes running bad its because the header bolts come loose, gaskets stuffed there, or the seal between pipe and muffler has loosened.
The header pipe into the head is a weird fit. i bought loads of the gaskets but also used gasket glue which works really well too. You can put your hand near the header when the bikes running and if you feel air pumping onto your hand, that seal isn't sealing.
Every now and then my pipe loosens somewhere causing leaks and i quickly fix it. first thing i notice is the bike sounds different, worse, and then performance. coughing spluttering etc.
closing the exhaust system up turns into Burt Munros Indian Scout.