I am not sure if this engine is equipped with the SLOW feature , if the engine is overheating it will activate and shut off firing on some cylinders..Remove the T-stats as test ..
This year also has a diode in the harness..
Test for SLOW
Engine will not rev beyond 2500 RPM:
1. Use a temperature probe and verify that the engine is not overheating.
2. Disconnect the tan temperature wire from the pack and retest. If the engine now performs properly, replace the
temperature switch.
3. Make sure the tan temperature switch wire is not located next to a spark plug wire.
Simply test also hook four of these in line and run the engine gives you a CLEAR visual if you firing intermittently or not during the symptoms
http://www.harborfreight.com/cpi/cta...temnumber=4424