R Anestis,
The EZ will not raise you EGT's too high. The EZ comes with a boost elbow, and you can adjust the fueling to come in about 4 lbs of boost, or 10 lbs of boost and I think the 3rd setting is around 20# of boost, which will help control the smoke. It also advances the timing and fools the computer into thinking that the boost is below 20#, but allows your boost to go up to much higher. Reguardless of what setting you have it on, it will give you the same amount of fueling and timing. The fuel will just start at different boost levels according to the settings. Most people who use the EZ are getting anywhere from 45 to 60 HP increase. The EZ installs in about 5 minutes.
The PE will raise the EGT's while towing above 1350 degrees. It has no timing advance. It has a buttom that you can switch power levels on the fly. You can add from 50 HP to 100 HP with the push of a button. The PE installs in about 45-60 minutes and has to attach to the injection pump wire. (Which is a real pain in the butt).
You will need a box to fool the computer so it doesn't start defueling.
As far as your trip computer, forget it, the MPG has never worked properly on most of the Rams out there.
I highly recommend you get gauges with either box you decide on. I got the PE first, but I didn't tow anything.
I'm not sure where you are headed as far as HP and performance. If you just want to improve performance while towing, I think I would go with the EZ and gauges. And then like I said in my previous post get injectors and help save the wear on the injection pump.
Can't help you with SPA gauges, I have UltraLites.