Your a 85 so i don't believe you'll have the fancy fuel filter head with the heater in it as the post above is talking about but on the old style filter heads there is some sort of stupid return line or something that I've had issues with on mine (1983). I would get a kit to replace your return lines and your issue may be fixed. I had the exact same thing happening where I would get a "burst" of power out of nowhere and the truck would kind of take off and then it would kinda settle back down as i kept driving. Replaced the injector return lines including that line and haven't had that issue since.
I was thinking it was my IP as well since I'm running the original IP and Injectors with 137,000 miles but fortunately that fixed it so before you try the IP try replacing the lines or eliminating that line. It isn't actually necessary and theres a write up somewhere about deleting it. Also I'll note that I didn't ever have any visible leaks on my hose the system was just drawing air in on mine.
Before someone jumps on my a$$ I am not saying it isnt the IP as it certainly could be but air intrusion is really common on these trucks and this was my experience.