Torque is the most important parameter for 0-60. If you believe Dinan claims that the top torque with the CAI is 350 ft-lbs, then this is just 16 ft-lbs less than the M5 (both at around 4000 rpm). I do not know what has happen to other people with the chip mods, but mine has noticeably greater available torque. I also want to point out that some 540iA owners on the 5-board (Jimmy) have claimed measured G-tech times of 5.1 seconds with the Dinan mods (although I suspect that they are Dinan enthusiast which biases their reports)

However, the bottom line is I am just guessing and will never know unless I take it to the track or G-Tech it.

I do agree with your feelings about Dinan. They charge too much (especially the supercharger and drivetrain warranty) and misrepresent their warranty and they also use inaccurate scare tactics by claiming that using other tuner's products voids the BMW warranty. The truth is their products are treated no differently by BMW than anybody elses. I did talk to Racing Dynamics about a chip, but they did not have one. Therefore, my only choice was Dinan.

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No offense, but cutting 0.5 s needs more than just engine and transmission chips. Let's compare E39 540i 6 sp and M5 for an example. Those 2 cars differ in about 113 HP. The 0-60mph time differs in 1.0-1.2 s. M5 has 3.15 diff versus 540i 6sp's 2.81 diff. It takes 113 more HP and 12% larger differential ratio to cut 1 s. That's even for E39, a lighter car than E38. I would say thay your claim is too optimistic. In addition, some actually report HP lost in dyno test after they install CAI and new engine chip.