I don't have closed loop and have still had 35 mpg at a steady 90 all the way from brum to Watford gap services. As long as I keep it off boost and accelerate GENTLY its surprisingly good on fuel. This was worked out from brimming it before I set off and then brimming it again at the services.

For the cost of closed loop/coilpack etc am I really likely to see much of an improvement?