It will work with I4. The sensors may be in different locations, but it can be done.
As for running it all the time... I'm just using a 100K Ohm resistor right now. 24/7, No pot. I don't even have the temp sensor installed anymore, just the resistor. As it is, my car always thinks that the IAT temp is exactly -20C. I've been running like this for 2 weeks now with no CEL, and no problems. I haven't tried running this with regular gas and I don't plan on it.
The car is definitely more responsive like this. Torque steer is harder to control at WOT, I find myself spinning the tires by accident, and it now pulls pretty hard all the way to 6750rpm, instead of dying at 6000. It's also less affected by the outside temperature, because the ECU doesn't have to (over-)compensate by retarding the ignition timing anymore (to prevent pinging with 87 gas). Cold air is still better than hot air because its denser, but this helps
This mod will also do things that a mail-order superchip won't. It will enrich the A/F mixture slightly, which only a custom-burned chip can do. It's obviously less precise than a custom chip and it's cannot replace a good dyno-tune by any means, but I believe that it will provide all the gains (maybe more) of a mail-order pre-programmed chip for about $0.49.