All EFI'ed vehicles will give problems at some point, as Glen mentioned locate the O2 sensor and check for connections, next check the 'air box' connection, check all accessible connections on and near the throttle body. However, please provide a little more info such as... where you offroading near water, is your rig a mall crawler? , when was your last tune up .ie. plugs, wires, cap, oil and air filter etc.
All this info helps to find the source of the problem! A well tuned EFI will run problem free for many miles, A WELL TUNED EFI !
DanS