catalytic converter

I are wanting to take out the catalytic converter and are wondering will this upset fuel/air mixture on a 2008 bandit 1250

No it won't. Just be mindful that emissions will be affected, so if your bike gets tested at some stage it may fail.

A couple have done this and reported it's a pain in the bum getting all the honeycomb material out. Might be easier getting the hole section cut out and replace with new pipe.  Either that or go for aftermarket headers. 

Not sure about tuning effect, I would have thought the less restrictive exhaust breathing would make some difference. 

You might want to remove the PAIRS plumbing as well,  I reckon there might be some additional exhaust popping.

thanks,

might be easier to get after market pipes and leave standard pipe alone in case emissions test then I can put standard pipe back on

I did the same with muffler, got another rear pipe and cut off standard muffler and welded a cobby on which is free flowing all for about $160 which includes the spare rear pipe

the cobby works well, nice sound and better power, I do get small amount of popping when backing off.

I was told to put a small resistor on the exhast sensor to stop this. this sensor has 4 wires 2 for the heating and 2 for the sensor, is this right ?

The popping is caused by the detonation of the air enriched unburnt fuel in the hot exhaust.  The extra air is supplied by the PAIRS plumbing - it's part of the emmission control systems. By removing/blocking off the air the exhaust is not at the right mixture to allow detonation (well a lot less detonation/popping than with the PAIRS working). 

The issue with removing the factory O2 sensor is that it upsets the ECU with it not getting the correct voltage level,  this can then cause a problem with tuning and in some cases make the Fi light come on. 

I don't have the correct wiring or size of the resistor to replace the Sensor but it's been mentioned on here so a quick search should provide the solution.

Factory headers are double walled. Inner diameter is drastically smaller than outer. 
After market header are worth every penny. 
Unleash the power!!

The popping you are getting is from the Pair system. Real easy to fix, just pull the tank and stuff a marble down the Pair air supply hose from the airbox. 

I have fitted Arrow headers. Its unleashed power but does need a form of fuel control. Stock mapping wont work as they are already to lean. 

I just happen to be selling a Holeshot fuel controller for one. 

Im taking mine in next week to be flashed on the dyno as Im heading down the path of more mods to the motor.