I don't usually work on anything that small but I know a 2.8 has a reputation for being a piece of crap. The 3.1 is a much better engine. Neither engine is potent enough to belong in the hot rod talk area but then we don't have a forum for sidewinders.
My guess would be that the computer isn't set up for the sensors on the 2.8.
Good luck and if you ever get a chance to buy another 2.8 don't do it.
AL