E-tec not running right

[Dueck]

I hope someone has had this one before...

I have a 2011 e-tec. Had it ported and pollished, y pipe and can upgrade, same exhaust pipe. Did some minor clutching for the extra power. Machine is running good in 2195 feet, but in mountains it is giving trouble. Intermittent hesitation and sputter. first warm it up and it is good. Then as it gets good and warm
the hesitation starts almost stalls. I have to let off on the trottle completely. It's got me stuck lots...not fun. Once let off, Jam throttle few times, work throttle some and it takes off again. Some times it will do this multiple times, sometimes once. It eventually passes as long as machine is kept good and hot. Shut it off and have to start over.

Tried cleaning exhaust sensor seemed to be better for a bit. it's not the over rev limitor, dass key, or throttle safety. It's like more air flow has confused ECM mapping at higher elevations on mid range exhaust temps. Tried 76% and 30% av gas.

Does anyone have an idea on this one?

 

[SUMMIT TREE]

Just a shot in the dark but is it possible the clutch is not back shifting properly? If it's not its like being stuck in "high" gear and it will have absolutely no power.Or..... you said it works fine at lower elevation? maybe it doesn't know it's altitude and it's running way too rich or it doesn't know o2 content in the exhaust due to faulty o2 sensor and it's cutting back power to protect the engine? Also, now don't quote me on this one but i think there is a piston update this year of machine so maybe there is more serious issues like a shot piston ring.

If you already got er figured let me know cuz now im curious...

 

[Winter Brew]

Is it the rate of rpm hesitation? Different from rev limiter...the '11's were sensitive to this. If you can make it better or go away by clicking down on the TRA then that is the issue. Clutching has to be loaded pretty good on the 11 to avoid this.
Did it do it before the porting? Was it done by someone reputable with etec experience?
Might also try stock silencer, have seen that cure same or similar symptoms MANY times.