Also, Ive been reading some posts on here and am wondering if it is bad for me to leave my EZ box on level 3 all the time? Is this going to hurt my fuel system?? I think its about time for a non-pressure box :-laf
with regards to the transmission, I'm not the best source. EZ on level 3 is in the region of 50 or 60 HP which is moderate indeed, but it will put additional stress on the TQ and other components of the auto transmission. At this power level, there are few stories of transmission carnage to my knowledge, but just keep in mind that the auto transmission is the weakest link in the drive train.
But Since the original question here regards the fuel system, I can comment in more detail there. the short answer to your question is that I do not think running the EZ on level 3 all the time will hurt anything. the results of my testing suggest that:
1. pressures in the common rail are not excessive at this power level, but do come close to taking up whatever "margin" is there. After experimenting and studying this issue for the last 2 years, I have come to a my own conclusion that the rail itself, even the pressure relief valve, is not really compromised significantly at these pressures. Even on level 4.
2. the low pressure fuel system is also able to keep up with the EZ on level 3 (and even level 4). my experimentations show that the low pressure system is sufficient for approximately 100HP gain at the rear wheels, which is a little beyond the EZ.
3. Injector wear is probably of greater concern than the rail, but at pressures representing only a few percentage points beyond the original design, I do not personally believe there is a danger when pressures are below what EZ on level 3 or 4 would produce. That said, I have seen one autopsy result showing abnormal injector wear, where the truck in question ran with an EZ on level 4. this may be more related to (2) below (nominal rail pressure increase)
My personal opinion, after reviewing numerous pressure modules and studying the rail pressure behavior of all of them using my custom gauge, is that there are TWO factors of interest:
(1) maximum rail pressure, obtained via aggressive pressure fooling to achvieve more than approximately 70-90 horsepower gain at the rear wheels. this causes the rail to run too close to the pressure relief valve set point. this over-uses the valve (which I have come to believe can normally open under severe rail conditions anyway, even stock) and introduces excessive stress to the rail itself. just my opinion here of course. I personally am nervous about using pressure fooling to obtain more than 70-90 HP, but rail pressure increases of this nature are only on the order of 5-8%. no big deal, especially considering that it does not happen very often (WOT only). Interestingly enough, the WOT run itself isn't the problem -- its when you back off suddenly and the pressure in the rail has no place to go
2. aggressive pressure fooling to obtain a fuel economy increase causes a significant increase in nominal rail pressure (quite apart from WOT maximum rail pressure). for example, highway cruising might run at 12-15K rail pressure (stock), while an aggressive pressure box will run at well over 20,000 psi. Such an increase in rail pressure can easily be 50% over stock (say, 12,000 psi to a 18,000), which is perfectly harmless to the rail but puts an extra, constant stress on the injectors.
I find that the EZ on my truck (level 3) produces approximately 30% increase in nominal (cruising) rail pressure and is not what I consider "an aggressive pressure box".
all tests performed on an 03-04 (305HP) truck.