Help needed
 

Have a problem with my 88 RS 2.8 MPFI, 190050 miles on clock. this has been an issue for some time. Starts up OK can drive maybe 4 miles and then starts bucking, can not give any gas pedal that just makes it worse. Last summer I went to visit my sister in Pa., 500 + mile ride, left home got 6 miles and it started fighting me as usual, this went on for maybe 30 miles,
could only go 40/45 then it cleared up and when I got back home I had traveled over 1400 miles not problem at all, I have found out if I drove everyday it would act normal, but
not use it for couple days and then it reverted back to old routine. I have replaced the TPS and MAF with no improvement. I am a loss for new ideas. any help welcome.
I bought this car in 93 with 50000 on clock garage kept and stored in winters, normally late Nov. to mid Apr. I live in Northern NY state, near Canadian Border, Winters up her usually long and cold .Been a very could car for traveling ,have several 700+ drives in a day ,And not really beat from the drive. Thanks in advance for help