Most likely, there is a governor in your Jeep that probably tops at
75MPH. You should take it off by replacing it with a racing chip,
like the ones Jet Performance sells. There are other chips out
there so just research. Think of your problem as if it wasnt govern
and 200 was your top speed and 55 was 185. The engine can only do
it also sounds like it may not be down shifting when you floor
it. You should check your transmission fluid and see if its low.
That would be one cause. If it is a straight 6 it just isn't
desighned for speed. Well, good luck with your speed!