I have an 87 W250 that boggs down when in gear. She was running fine and shifting great then this started out of the blue. The previous owner put an aftermarket edlebrock 600 on it and removed all the emissions. She still revs fine in park and neutral but as soon as I put it in drive and press the gas she boggs and dies. If I don't press the gas while in drive she will idle and drive fine. It feels like a vacuum leak but I don't know where to start looking. Any help would be much appreciated. Thanks.

 

I would check all the emission ports and make sure everything is plugged. I had the same problem and found an unplugged port. Let her idle 5-10 minutes and drives just fine. I'll repost with a picture of where my problem was

 

Spray around the carb and carb base with starting fluid while the truck is idling. If there's a leak, this will show you where it is.