I had a similar problem on the Jeep GC (<img src="/forums/images/graemlins/ignore.gif" alt="" />) I used to have. Turned out to be a fuel delivery problem. A new fuel filter and a tank of gas with good injector cleaner fixed it. This may not fix your problem, but it's cheap and easy to try it.

'97 Montero 'LSR' - 4.6 gears & factory rear locker, 33" Procomp muds on 15x8 steelies, 50mm coil spacers, T-bar crank, Airlift, sans rear sway, 50mm rear frame & fuel tank lift, Aisins, ARB front bumper + 10k lb winch, 50mm DIY body lift, rock sliders, cut rear quarter panels...