Bucking occurs at a frequency of about 1 time every 2-3mins
Constant Throttle

 

Try undoing the last mod you made.

 

I think I found the problem with the car

The Secondary air pump hose was just about to come off the air pump valve on the back of the intake manifold.

Have not had a any sort of problem since I fixed that hose connection.

Pulled the ECU codes none stored and none pending.

Also did the MAP TSB and put a zip tie around it.