Need help please stato problems !urgent!

[vigi88]

For the past couple days ive been having some problems with my WH super6 statesman, for some reason when i turn the car on for the first time in the morning it feels like its about to stall (and has stalled one of the mornings), i had this same problem 4 months ago but that was on hot days, the result of it that time was the fuel pump, i really doubt it would be the FP this time since i had a new one put in few months back, the only thing that i can think which could be causing this problem is the "Cold start Sensor", but im not 100% sure, if anyone has ANY ideas please feel free to post them, i need this problem fixed asap.

at first i thought it was the cold start sensor but now it seems to be doing it during the day too even when ive been driving for a while, it seems to only do it when im stoped at the lights or something, could maybe be the oxy sensor or maybe the idle speed motor maybe?

any ideas would be great
thank you

Another thing is, ive been looking to get a smaller pulley for the supercharger, i think im running 7PSI, the new pulley will give me 10PSI would i need to do any other changes to the engine if im upgrading the pulley? or can i just chuck it straight in, without messing anything up in the engine?