I need help and I need it fast. Hope someone can help me out here. I have a 1998 Buick Lesabre with the 3.8 series II. Car started out dying after about 20 miles. Restart it and it would go another 10, 5, and so on. Here'* what has been replaced to try and remedy the issue:Plugs, Wires, Ignition coils, ignition control module, MAF sensor, MAP sensor, EGR valve, IAC Valve, TPS, PCV, Fuel pressure regulator. After replacing all of these to no avail, I replaced the the fuel pump and filter. Now the car will run great on the highway with little to no trouble at all. My problem now is in town driving. Every time I stop the vehicle it stalls. When I get her started back up again(starting it in neutral) I have to throw it down in first to get anywhere and shift to get up to speed. When it does this dying it will blow out black smoke from the tail pipe and run like it has a miss. I'm getting no DTC of any sort and my live stream data does not indicate anything abnormal. My biggest problem is, I live outside the States in the Bahamas and finding an alternative means of transportation is out of the question. If anyone has any suggestions that would greatly be appreciated. I have leave this vehicle so my father will have something to drive when I return to Kansas and he is incapable of working on it. Thanks.

Black smoke usually is an indication of it burning oil or really rich fuel. I would recheck the fuel pressure regulator.

How is braking on the vehicle?

Braking is normal. I would say that the vacuum draw from the booster will occasionally effect it. Car is definitely running rich for sure. Gone about 60 miles on a quarter tank. Another thing I noticed is a thumping coming from inside the tank. Could a bad regulator create enough vacuum in the tank to create what I am hearing. Everything, including the pump and hanger assembly is new and all held firmly together.

I've also ruled out leaks around the intake. I know these were notorious for that.

I can smell a hint of fuel at the vacuum line coming from the regulator, but not like a leak or anything. Can the regulator allow for to much pressure at the fuel rail? That regulator was replaced about 8 months ago with a BWD regulator.

I think the test is remove the vacuum line going to the fuel press regulator and idle it up to about 2000 rpm for about 2 mins and if its bad fuel will start leaking out the vacuum line the regulator is bad
I would say actual it is if you smell fuel at
the vacuum line its being sucked into the engine from that
about 99.9% chance from what read hear

at higher rpms the highway
it can handle the extra fuel its sucking in
at stop in go low rpms it cant handle all that fuel
so it stalls out and all the black smoke on restart

Hopefully one of the parts stores here has got it in stock. I'm limited to AID(NAPA) and a CarQuest. It will cost me double, but that seems to sound like the culprit. I'll give it shot. As far as the thumping near the tank, I may have just put the tank in slightly cockeyed in a rush to get it in. Time is not on my side.

be sure to test it like I said first but I would almost bet the rubber diaphragm has a crack or pin hole in it