Ditto the others as well but I find both the outside and road temps can raise the pressure. I have the pressure pro system as in 06 it was the only thing on the market. I like what those are saying about the units where you can replace the batteries in the sending units. I have had my system for almost 5 years and only using the sensors when towing they are still working good. However, some day I will have to replace them.
Best thing is don't care what system you have I think it is well worth the money in the peace of mind department.
George and Debi
2006 F250 PSD, 2005 PF30CK