We are stumped a little ??

[Eric K]

I would swap parts back and forth until you find a signal.

The head is a straight forward swap, just make sure you have adequate squish clearance.

The pipe is an easy swap.

The carb is an easy swap.

This is the cheapest way to go on your search.

 

[101racing]

I would swap parts back and forth until you find a signal.

The head is a straight forward swap, just make sure you have adequate squish clearance.

The pipe is an easy swap.

The carb is an easy swap.

This is the cheapest way to go on your search.

Carb on the 08 is RB and also the head. The 08 actually has more compression than the 06. The carb on the 06 has the LTR jetting.
We did swap pipes and there was no difference.
Swapped CDI's with no difference.
I have to believe it is definitely a porting difference. The power valve is obviously different.