Can a tank gauge lose pressure?

[ybn533]

Hi,
I have a hot start problem with my 00 boxster S. it seems that it's losing fuel pressure after an hour and it starts only on 2 or 3 spin.

I already bought a new fuel pump but my mechanic indicate that I should buy also the tank gauge, carbon canister and vent line.

It seems that he doesn't know where the problem is and looking to change all the parts to eliminate the problem. if it what cheap, I would go for it with no problems but these parts are big on $.

Already got the fuel pump, so what to do now?

Thanks
Yaron