3 Cylinders cut off while driving

Driving my 98 trooper 3.5, runs really well. all of a sudden 3 of the cylinders on
the right cut off and I loose power. Few seconds later same 3 cylinders come
back to life and runs good again till it does it again. We've diagnosed it down to
the 3 cylinders on the right. Now trying to see whether it's the coil(s). Any
ideas??