I've got some schematics for the 97, but not the 98....  Check to see if you are getting power to the MAF or any of the other sensors.  I have had limp mode occur because of one power wire not hooked up..  I had a good friend and wiring guru for the RZ's come and take a look.. 20 minutes later purring like a  :chillpill:kat.  He said none of my sensors had power and the motor was just in limp... 2500 rpm rev limit and idling rough.