1996 Jeep Grand Cherokee misses on the highway, not on surface streets

Question

My good old Jeep Grand Cherokee, 1996 and original owner with 274,000 miles is, the last few days on the freeway only, missing and semi stalling. No check engine lights, all fluids etc. are fine. I hope there's a maintenance trick someone know that doesn't involve replacing the fuel pump.

Any ideas out there?

Thanks