I had the same problem on my massive trip down to LA (from Canada); LR Dealer at Santa Barbara said they thought it was an aging VSS (vehicle speed sensor) - as my vehicle is a 1997 SE7 Disco as well. Apparently, when the sensor gets senile it can think that 60 or 70 mph is 110 mph and that's when GEMS says "no way man" and it starts cutting power to the odd cylinders I believe - it feels literally like the engine is staggering or, in aircraft terms, feathering - most disconcerting on the ever-busy I-5 on the way to San Diego from Annahiem! But the problem I have with this is that a senile VSS is supposed to throw codes at you (such as a P0500 - vehicle speed signal out of range) and I never had any related code, whatsoever, slung my way! I worried about fuel pump and fuel pressure too but, again, there should be identifying codes if that is about to give up the ghost too. So, I looked further to John Robison's LR Service site and I found out that this problem could possibly be caused by sticky exhaust valves - not a pleasant or cheap thought either! I am not saying definitively that this is the problem - but if you have a clacking exhaust lifter you might want to give this some hard thought!
