'94 Ford Van Question

Hey All,

The Van is a 94 Ford with 351W and E4OD tranny.

The symptoms;

Sometimes the engine "races" as though it were at a very fast idle.
(Fast enough to keep the van moving at 30 to 40 MPH) 

Sometimes "pulses" at speed as well as when accelerating, (as if I were
fluttering the accelerator pedal).

I'm thinking oxygen sensor???

Any and all input welcome here.....

Thanks,

Kevin V.