Oh dear.

It has absolutely nothing whatsoever to do with the greys mate, only the setup and the map. Greys are fine for 30+MPG on any Std Comp YB motor. In fact, so are 83lb siemens and cams etc for that matter. click me.

You cant rule out the fact that you may well have faults as well, so unless you are certain that she is setup perfectly, and the rising rate reg etc is all set and working fine and all sensors are doing what they should do, i would recomend you do as follows:

Order the 55lb Siemens closed loop mail order chip from me.
Read the comprehensive instruction on how to set it all up and then fit it and get it working. Finally, test her for a while and then drive her to us for a setup and custom tune of the software if required. The reason i advise you fit it yourself is:

• A) You save us time welding boss in exhaust, fitting inj's etc meaning we can complete the job in a day.
  Ideal when your from London as i recall you are?.

• B) You can build up some feedback over the weeks of how it runs and any concerns you may have that we can deal with directly on the day. Cold start / cruise / throttle response / economy / etc.

Hope the above makes sense Simon. We can of course fit it all for you if you would prefer, but I simply cant guarantee to have it done all in one day if the software requires significant alterations. That said, that would only be the case if your engine spec is NOT what you think it is. If its close to what you think it is, then the chip will be within 90% of perfect from the moment you fit it.