Let me add to what 2cool said.
I wrote the install guie for the Jet module way back in winter 2000.
I'm an electronics and driveability specialist as well as an ASE master certified tech. I also write articles for automotive magazines.
I did extensive track and road testing of the JET after writing the install guide.
It does add significant power..... but only at part throttle.
The sensors it tricks are not read by the PCM above 85% throttle. So.. at wide open throttle, WOT, it isn't even working!
The same can be said for the simple resistor mods. They go across the temp sensors and they aren't used at WOT.
The PCM in the PT goes open loop and uses a preprogrammed fuel and ignition curve. It's programmed to go WAY rich to protect the drivetrain. Part throttle timing goes as high as 37 degrees advance. WOT will not go above 24 degrees total advance.
The PCM program add limitations that the aftermarket can't overcome.
I beleive the JET module has been discontinued. They certainly won't reply to me after I actually tested their junk.
I've worked with JET on other projects. Their modules and chips do work with PCM programs that aren't as limited as the PT.
Here's 2 base runs. Back to back showed a 3hp variance.
110hp and 113hp with an automatic trans.
This is the same DynoJet chassis dyno 2COOL used.
