Welcome to the forums! Post up some piccies and specs on yer current truck (engine size, type of transmission, etc).
Have you looked into gitting and OBDII scanner like an Ultragauge, Scangauge II, or one of the bluetooth/wi-fi based ELM327 readers that you can find on eBay fer cheap? Yer Mazda should be OBDII compliant...
How many batteries do you carry on average? Have you beefed up the rear springs at all?
Have you checked out any of the aero cap threads?