Vacuum boost canister

[Mrturner1]

Talked with a transmission guy about getting my stall converter and tranny cooler done, and explained about my th400 shifting from 1st to 3rd when at wide open throttle, but not when just cruising. When cruising it goes through all 3 gears perfectly. He says my cam is large enough that I need a vacuum boost canister, and the lack of vacuum is why the transmission is shifting too soon.

So who makes a good canister setup? And how hard is it to install, I'd like to save on the labor costs