Gutted muffler, now 02 inactive.....major power loss.

Bike is a 2005 xb12r.

Cut up airbox with stock filter.
Wrapped headers.
gutted muffler w/valve welded open.
ebr race tune.

Bike had 0 problems before the muffler was put on. I pretty much did the common muffler gutting, minus the packing and running two tips. The bike feels like its trying to pull a car now. If you crack the throttle at idle, it almost stalls the motor.

Took it out for a ride after a tps reset. While cruising it threw a 02 sensor inactive code. Bike rode exactly the same after the code tripped.

Going to make sure the sensor is getting voltage, then check the sensor itself. If both are good, what would you suggest as the next step? Could all of this be caused by the muffer?

Once you get the o2 figured out if it still does the same thing pull off the muffler and take it for a quick spin. It could be that you hurt the exhaust flow with somthing you did inside the muffler

open exhaust and intake kills the bottom end grunt on these bikes, something about exhaust velocity and fluid dynamics or some other shhhtuff, but I think you have flooded and burnt the O2 sensor, like a car with a bad plug, or at least fouled a plug, I'm sure one of the more experienced tuners will chime in.

The EBR race tune may not be optimal for your bike. Since you have an '05, why not throw your original ECM back on (I'm assuming you have an EBR ECM from your "EBR race tune" description) and use ECMSPY to do some datalogging and achieve a 'proper' tune for your modified can? Unfortunately, you're not likely to get much of your previous bottom end performance back with a gutted muffler, even with a tune. Most who go with a gutted muffler do so for the increased exhaust volume, not performance. A good tune might reduce decel popping and help smooth out any dips in your mid-to-upper power curve, but there's only so much you can do with a gutted exhaust. I've got several friends who've made similar complaints about their performance after gutting their mufflers. I was able to tune their bikes and help a little, but nothing drastic.

Any chance you didn't perform the TPS reset properly or accidentally left your IAT sensor disconnected when you modified your airbox (been there, done that).

LOL turns out that when I pulled out the exhaust flap line, it unplugged the rear cylinder coil. Hence the reason the bike wouldnt get to operating temp at idle and it thought the rear o2 was inactive. Let me say the bike pulls harder now everwhere in the band. I was expecting some low end loss, but its not the case. Thanks for the input guys.

i realize you fixed your problem but i gotta throw a couple pennies your way to chime in with performance. I have an 09 xb12R the sweet ass cherry bomb scheme and the first thing i wanted to do was make it louder. well anyone with common sense knows that any kind of internal combustion motor is basically an air pump. if you increase the amount the engine can exhale (exhaust) you should increase the amount the engine can inhale (intake). so i took my airbox and made it look like swiss cheese. i also put a K&N filter on it. Then i took my muffler off.. watched a couple videos on you tube as to wherei should cut the muffler and did so according to the video. i only pulled the guts out and didn't mess with the valve although when it opens it doesn't make a difference. At first when i fired it up i was like holy $h!t man this thing sounds nasty. that feeling of satisfaction quickly diminished as soon as i took it for a ride and realized the pull wasn't there anymore. i recently ordered an erik buell racing ecm.. i wrote them first, explained what i did and they said i should order an ecm for a drummer ss muffler because gutting the muffler is pretty much what the drummer is. This is my second xb12r my first being an 04 and lets just say that now my bike pulls harder than i have ever imagine. for any of you that have ridden the xbs alot and wheelie them constantly know that third gear wheelies are a myth unless your shifting into third while still in a wheelie. well now the bike comes up in third gear with the assist in the clutch and a minor rev but nonetheless it is an ANIMAL!!! a friend of mine has an xb12r with a kn, a jardine, and an buell factory race ecm and doesn't stand a chance to mine. he took mine for a spin (yikes) and when he came back he couldn't wipe the smart ass grin off his face. Gutting my muffler and the erik buell ecm was the best thing that ever happened to my bike!!!