Hey guys, I have a 2000 V6, and I'm about to buy either a s/c or a turbo, and I know I need higher pressure fuel injectors, but how much? Stock are 19lb, but would I need 35 lb? More or Less?

The green top 42lb fuel injectors will be more than enough for a stock v6 with a blower (or two) plus they will bolt right in.

Your stock are not 19lb.
94-98 are 14lb
99-04 are 21lb
GT mustangs, Crown Vics, T-birds and other apps share the 19lb injectors while NA cobra's and MKVIII's have 24lb injectors. The Mach1 also has an EV6 style 24lb injector.

98 and older is EV1
99 and Newer is EV6
In a nut shell....

2005+ GT'suse 24lb EV6 injectors.

Hmm. Does anyone know what a turbo would do to gas mileage?

So long as you keep out of the boost it won't affect gas mileage at all.