no start after cold and sometimes hot soak

[great white north]

My 06 apex gt mcx 260hp kit doesn't start when cold and sometimes after hot soak. It has a brand new fuel pump relay, upgraded fuel pump(external walhbro), new plugs. When cold ,it will fire, and sometimes try to idle for 1 or 2 seconds and then stall. It will take about 10 minutes of multiple tries in order for it to start and then it takes a while for it to accelerate. Anybody have problems with these upgraded pumps because, all these starting issues seem to have begun since pump upgrade? Also, any body seen the coolant temperature sensors fail on these sleds yet? After it is at normal operating temp, you can shut sled off and start immediately, so I am skeptical about intermittent pump failure because when warmed up, it pulls very hard. I should mention it always will crank but not start.
Any suggestions would be appreciated.

 

[SPEED]

What fuel are you running?

 

[great white north]

sunoco 94 with nos max octane boost .

 

[canuck5]

In the extreme cold I have seen something similar. Had mine on my deck on the way home from mountains and when I got home to the bone chilling -30 it would start and quit few seconds later. Has done this to me twice only in the extreme cold and i never ride it around here. Drag into the garage heat it up and no issues it threw a yellow engine code but LCD display wasn't working very well at those temps. Never an issue in warm garage or even up to -15. I'm also running Half race fuel.