Was it definitely a genuine bosch pump? There are far too many fakes about and unfortunately the 3i style external pump is one of the easily replicated types.
2 other things i'd check - the non return valve on the pump itself, did you install a new one with the new pump or swap over the old. I've had one of these make some odd noises before, tho admittedly drive time/heat didnt impact, it was there from start.
Secondly, the fuel accumulator - this irons out pulses and most definitely has influence on things such as vapour lock etc.
Lastly voltage - have you checked to see what voltage is at the pump? The current draws on these are high, the wiring breaks down, and heat will only exacerbate that, it could be struggling with low voltage