I'm thinking of getting the Zexs kit for my car and I was wondering should I run a 50 shot for a while than upgrade to 65 shot and later a 75 because I want a 75 shot but I have stock intern and was wondering if I should take it slow so I won't harm anything or just go with 75 right off the bat

You could just pop in the 75 jets and it should be fine. However, to be on the safe side that everything is working correctly... you may want to start with the 50 jets and check your A/F readings and such.

I just hooked up my zex kit today and started with the 65 shot. Made a couple runs and checked the plugs and they are fine so I'm movin right up to the 75 shot. You would be cool just starting with the 75 shot i believe. The zex kit is the easiest thing I've ever hooked up.

With a 10 shot differnce its not gonna make that much of a difference, go straight for the 75.