Is there a relay to provent maximum acceleration the engine?
Yes. It has limp mode and a Governor both. One to prevent over- speed and the limp mode to prevent further damage to your engine in the event of a transmission problem - http://www.jeepsunlimited.com/forums/showthread.php?502505-Limp-mode - http://www.jeepsunlimited.com/forums/showthread.php?442673-42RE-Governor-Pressure-Solenoid-and-Sensor-fix
But re-reading your question Soulmanblue, if you are asking if it has some sort of device to keep it under- powered.. well, no
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