88 cherokee inline 6

Kangaroo start in low gear cruise without problem all day at 60-70 kms Hesitates at high speed .Lack of acceleration and power drop off climbing any grade.

Do you know how to save this vehicle from a bullet?

Knowing how many miles on the vehicle and what, if any, maintenance has been done might help.

Lack of acceleration, power drop off climbing a grade, etc. could generally be caused by one of these.
Worn out engine (run compression test)
Weak fuel pump and/or clogged fuel filter (latter will kill the former)
Partially clogged catalytic converter (tested with a vacuum gauge)
Retarded ignition timing

Those are the most likely suspects anyway.

Thanks a lot will try the above and let you know what happens.Blocked fuel filter left me on the side of the road not so long ago so perhaps pump is now toast.