So I did a street tune on my 00 gsr using crome and put it in a skunk2 ecu. It ran fine and all the rpm limits (vtec, rev limit) were all where I set them. Recently I switched the exact chip into a chipped p28 and it still runs fine with vtec in the same place but somehow the rev limit comes at 7900 instead of 8200 where it used to be (where I had set it). I figure either through some black magic this ecu sends a slightly different signal to the tach so it reads lower or there's something subtly wrong with it. Both seem very unlikely so I'm just wondering if anyone knows for sure or has any other ideas. It's obviously not a serious problem but still very curious.

Thanks in advance