The fuel pump upgrade was a common scapegoat for the poor results achieved from the piasini tune, I know of several MPS 3's running Xedes upward of 200 fwkw that have never required the factory pumps to be upgraded.
The CDFP pressure can be monitored and logged with a Dashhawk, if you know of anyone with one you can borrow, go for a good run and log the pressures, from memory they should sit around 1500-1700 psi, if you dont have access to a dashhawk I would encourage you to buy one prior to tuning so you can keep a closer eye on things post tune.
Otherwise I would do the tune first, if you find your car is cutting out in high load / rev scenarios then look at changing the pump, otherwise you will just be wasting money replacing a perfectly good part.
Nearly all men can stand adversity. But if you want to test a man's character - give him power.
Abraham Lincoln