Dancing tach, Runs like crap

[FrankR]

Hello folks! First time posting here. I have a 94 Silverado K2500 4x4 with the 350 tbi 175k miles. I purchased the truck about a year ago and have been pretty happy with it until last week when it suddenly began giving me a world of trouble. It started with the tach needle bouncing around while cruising down the road. It would jump up and back by 1-2 k. At first there didn't seem to be any noticeable stumble associated with it. Then it got worse and did start stumbling. Now it is almost undriveavle. It appears to do it only after it gets good and warmed up and only when crusing at a steady speed, smooths out when accelerating. It doesn't seem to be transmission related because it will do it in neutral and park although it feels like it is shifting into od too soon now. I did a tune up when it was first purchased so the plugs, wires, rotor, cap and fuel filter are only a year old. Also I installed a tbi rebuild kit about 2 months ago. I need to get this figured out because it's my daily driver and I dont have the money to have it towed to a shop so they can troubleshoot it. Where to start? Seems like it could be a dozen things. Thanks!

[FrankR]

Would a damaged knock sensor cause this? I did damage the connector while wrestling a new starter into place last week. I'm starting to suspect fuel delivery. I pulled the air cleaner and watched the spray pattern and it seems like it's pretty coarse. I can see droplets rather than a fine mist. Could a dying fuel pump cause these symptoms? I dont have a fuel pressure guage to test pump pressure output.