I've had the V-Force on my 2000 Mitsu Eclipse. JET said that I would get 10-15 HP. I had it dyno'd and did not see any gains. What modules like v-force do is that they tricks the computer into thinking there is more air coming in than there actually is. You can simply step on the throttle a little more to accomplish the same thing.
With most modern cars when you go WOT, the ECU goes into the open mode where it goes to a default fuel map. So even if the V-Force is giving the ECU a false reading (higher count of air), the ECU will not take that into account when it's running in open loop mode.
I would stay away from JET.