OT!! WTF is wrong with my '86 GMC

[Crank]

Okay, just started like 30 minutes ago, driving around town exploring Jacksonville. My truck runs fine while cruising, but as soon as you go to slow down to turn or stop the truck bogs down REALLY BAD. Almost like it has a vacuum leak or something like that, but I havent been able to find anything loose. I messed with it in the parking lot, its weird, when I start it, it starts and runs fine, drop it into gear all normal. Comes out, idles up a hair, just like it always did. REV it UP, and let the idle come back down and its like its only runnin on 5 cylinders or something. The only thing I didnt check for a vacuum leak was the modulator. I could see that maybe because earlier today, I tightened the motor mount bolt on the pass. side... Can anyone help with ideas? I've messed with the timing and made sure all the plug wires are fine and connected... It's a 350 with a performer, 1406 edelbrock... everything ran fine before. Please help folks. Thanks
Brandon