a mate of mine was driving back with me after the drags. when he went to over take someone in 5th gear and when the secondary turbo went to kick in jerked (his words) so im guessing fuel cut checked codes and surprise surprise code 66 came up. it will only do this in 5th gear all other gears are fine what should i be checking first i know all about diagnosing code 66 but was wondering if someone has had the same problem