99 Grand Cherokee Larado that looses power
99 Grand Cherokee Larado 136,000 miles: if traveling 50 miles (distance) or more, totally looses power. have to push HARD on the gas pedal to maybe reach 40mph. if i take my foot off the gas, jerks me forward stopping quick. brakes are "right there" if i touch the pedal. when i stop there is a "hot" odor similiar to burning rubber, but not. if i let it cool down an hour or so, all is fine like nothing happened. runs fine on short jaunts. ??? what could it be ??? recently replaced water pump/serpentine belt/fuel filter/battery/ac recharged/oil changed religiously. still need this addressed but not sure what it could be. fuel pump? catalytic converter? vacuum issue? tell me where to start. please & thank you!