I agree that I usually doubt it when I hear somebody can get more than about 20-30hp total out of exhaust, CAI, and ECU- But, I also believe that Nissan and others do more than just market their motors differently, I think they do actually change the output. Very easy to do, just one or two changed ECU paramaters and you have a detune. You just don't want somebody who paid a premium for their Maxima pulling out onto the street and getting spanked by a lighter Altima with the exact same motor! That's one of the things I found appealing about the '45 vs. an X5 4.6is, the ability to get a lot more improvement aftermarket (since performance is a virtual deadlock off the floor).
As for today's ECU's, yes, they make the motors very efficient, but to get your perfect burn efficiency, you want to try to keep a stoichiometrically-perfect 14.7:1 air to fuel ratio (where the 02 sensor reads .45V, which is why you want to see constant cross-counts on either side of that #). BUT, max power comes from a lower air to fuel ratio, lots of debate as to exactly where, and it depends on the exact application, but somewhere in the 10-12 range is what I usually hear. Now, you burn more fuel because of the richer mixture, but you do get more power than the emissions-optimal 14.7:1. This all can be additive to the other factors which give today's engines higher specific output- things like variable valve timing, optimized fuel mixture, better and better flows in and out of the cylinder, etc.
Brnjugfx45, I agree with you- I don't mind spending the $700, but it better bring me optimal performance! Two questions on your converter- do you have a part# so I get the right one please, and what is the "Manual shift mod", is it part of the valve body work you did and what is the benefit? By the way, noticed you're from Philly, we just moved to Phoenix from Philly- really enjoyed the time we spent there- make sure you tear up the Blue Route for both of us, eh??
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