The coolant temperature sensor tells the ECU how much fuel to put into the car. If it's not working correctly the ecu thinks the car is cold and floods the cylinders. TPS not being calibrated correctly will make the ECU think that the throttle isn't being depressed when it really is or vice versa or it could even make the car think you are pressing the throttle harder than you really are. The ECU relies on sensors (maf, tps, cts, o2, iat, iacv, aiacv etc.)to tell it what the car is doing. lol

As far as plugs go, the 7e's are copper tipped, and the 7eix's are iridium tipped and pre-gapped perfectly. Iridium will last much longer than copper, so basically throw them in and forget about it (providing your tune is spot on). Do not get the 7eix-11's as they are gapped super high. Has this thing been on a dyno? Mail order tunes are great, but to really get an idea of what's going on you need to run it in ideal conditions with a wideband and log stuff. Changing something as minor as a catalytic converter to a test pipe and not re-checking the tune cost me a $4000 motor.