Jim - I think the 30 seconds has to do with the time it takes the ECU to
start getting info from everything. When I was having my issue my bus did
the same thing - ran strong and good for aobut 30 seconds and then would run
rough, rich, and also back fire. No power etc. I drove the bus home from
Grand Rapids, MI to Port Huron, MI (3 hour drive) having to put it in
neutral every 30 seconds or so and switch the key on and off to reset the
ECU. Not fun. It also wouldn't do over 45 mph.

I thought it was O2 sensor (which I was not running one) or AFM but also was
told to try the Temp2.

Again, this is just my experience. It may not be the Temp2 causing your
problems but that cured every issue I was having with mine.

Good luck :)

--
Thanks,

Jeff
'90 Carat (Grover)
'86 (We call this one Parts)
'78 Bus (Melissa) Patty's Bus