I have a 1990 740 turbo, runs great down the road, but dies when I pull up to stoplights.

voltmeter struggles when I first start it up although I have replaced the battery and the alternator tests good

I replaced the in tank fuel pump when I first bought it 6 months ago

Could this be fuel filter? Inline fuel pump? IAC?

 

Blip the throttle over 2k after it first starts and see if it charges higher. The Bosch alternators in Volvos are notorious for the exciter circuit and or wire failing. Revving over roughly 2k makes the alternator self excite and start charging. Fuel filters and pumps tend to show their "colors" under load, not at idle when fuel demand is minimal. Being a turbo, I'd start looking at vac hoses very closely. Check the iac hoses for sure. The extra heat that turbos produce, along with the system not only generating vacuum in the hoses but positive pressure when under boost makes for annoying vac issues for sure. As a matter of routine, I replace ALL the hoses when I buy a turbo unless they are obviously new. This may be criticized as a shotgun approach, but too many times I have examined hoses for leaks, sprayed carb cleaner and even used a smoke machine searching in vain for vacuum leaks. After swapping the hoses I usually will find one or more tiny, tiny splits. It could be other things of course but I'd rule out vacuum first.