I've recently started watching some of these modding shows on the Speed channel (I started to say "...on Speed", but figured that might be taken the wrong way). Some of those guys say things that indicate they are missing some important pieces of information or don't have a problem misleading gullible watchers to sell a product. I don't recall if it was that same guy or a different show similar to his, but the other day, they were hawking a product and talking about how important it was to clean and paint up the battery tray - that if you didn't, "it could lead to problems inside the engine" - their words, not mine.
"Since the throttle valve is nearly closed, engine has to draw air and work inefficiently causing a 'pumping loss' ". That would still be the case for closed throttle (deceleration) conditions since this device dodes nothing to open the valves of the cylinders that are disabled. But for low speed coasting and light acceleration, during which the throttle would be open some, the PCM would put more fuel to the cylinders that were not shut off, and to get the same power for maintaining speed or lightly accelerating, the pedal would have to be pushed a little more to provide them the air for stochiometric operation, so then the pumping loss would be decreased.
My guess is that there will be some fuel mileage improvement, but I would take any stated or implied numbers (i.e., comparing to production vehicles where cutting fuel injectors off is only part of what's done) for the improvement with a grain of salt.
I don't believe the bullet that says "Reduce wear and tear on your engine". That's just marketing hype for the gullible.
'98 LXi - Later Concorde gages (black w/ chrome rings)/'99 LX - LHS gages (white) - HIR bulbs