[FAR888]

I don't know whether your truck actually has any problem at all.

From your post, it simply sounds as if you have found the kickdown button.

..I exited a round about and put my foot down, the car picked up smoothly but then there was a very noticable increase in excelleration(sic)...

 

[FAR888]

I understand and was just kidding.

I'm no expert but could it be fuel related?

For example a component like your fuel filter being partly clogged?

Have you ever changed your fuel filter?

ps.

Are there any stored OBDII codes/"Check Engine" indicator lights?