What you are saying about your experience is similar to what my vp44 was doing. Here in the Phoenix area, for the last two winters, it would start and run like new. Power was down a little, but ran good.
As soon as the ambient temps started getting up over about 70-75 degrees, then it started to have an occasional dead pedal and would not pull. Never had the white smoke though.
I put up with it like I said for 2 years, then just decided that enough is enough, and bought a new vp44 from Midwest Fuel Inj. I liked their no core charge up front plan.
The new pump runs great. Very happy now with it and the new Rv275 injectors.