I have been told that the throttle slide in the new 2012 px125 has extra air pockets in it which makes the mix lean for the cat exhaust.
I had a sip road exhaust fitted the shop that did it have a dyno so have said they have set it up just fine with bigger jets. They told me there is a slight flat spot at the high end. I mentioned to them that about the throttle slide in the new px's but they said that it would not be a problem. I beg to differ.
I want to get a better throttle slide. the carb is an dellorto S1 20:20 but I am not sure what number slide to get. There are many listed.