85gt stallin, surging, and running like crap. HELP

I have been on vacation for a few weeks and not driven the 85gt much for a month. No AC and its hot here. I ran the car for a few minutes abut a week ago. Ran fine.
I installed 2 new gauges (oil psi and temp) both mech. and started the car up. Ran really good. Reved between idle and 450o rpm's. No problem.
I get in and warm her up yesterday, runnin good. Drive down the street for a 1/2 mile, no problems.
Make a stop and turn on to another road and hit the gas....................

Car starts buckin real bad. I think wrong gear, use clutch and check, Im in 1st. ok. Hit the gas, starts buckin voilently again. I rev and shift to 2nd. Nearly stalls. I hit the gas thinking maybe gas clog or somethin. engine About dies. I look at the tack, rpms jumpin up and down between 800 and 2500 about every second. Im freakin out now. Pull of the road, head back home in 1st the whole way 3/4 mile home. It was backfiring real bad, stallin, buckin.

I was low on gas and headin to the gas station. Gas has been in it for a month. Maybe funky gas. But I ran it a total of 20-25 minutes the previous days in the driveway with NO , absolutely NO hickups.

Im thinkin replace the fuel fitler. Maybe its clogged. I put about 3 gals of new gas in from my portable gas can. Start the car up and it contines to do the same horrible running. I spray some carb cleaner in the holley, no change. Engine torque'n over bad and car jumpin.

Any clue as to the culpret would be a huge help. I need your expierence guys. Thanks
Joe E.

Nope firing order in exact same order as it was before. I did nothing to the cap rotor plugs.

I was workin on the gauges last week. After I got them all installed I started the stang up and ran it for 20 something minutes in the driveway just to check for leaks in the new oil system fittings and coolant passages. I reved it up to about 4500 rpms numeras times. Reved and kept it at 2500 for a minute or 2 to see how the pis gauge would react. No leaks and no hickups. Ran like a top.

I go out the next day to go to the store. Start it up and let it warm up for 10 minutes. No issues. Ran great. I head down the street running fine. After 2-3 minutes of driving it started buckin. Then the rpm's jumpin bad, car wnatin tostall, etc.

Im gonna replace the fuel filter today hopefully. maybe tomarrow. Maybe do the cap rotor too. Check wires also. And blow out the fuel inlet area to as advised by a friend. Im also gonna get some more gas and some fuel stabolizer. Damn I hope this works. Im outa a car right now. Gotta steal one of my parents rides to get parts.. lol
Thanks for your help.
Joe E.