This should be what you are after;
http://forums.t5d5.org/topic/14158-t...ners-your-mpg/
I think after such a long time of you being used a diesel, the difference in economy may be a shock to you however, if you are generally looking to take it easy and cruise around then you should be OK.
Just also remember, these car are old, many may seem good but to ensure optimum fuel economy is extracted from them you need to ensure all the following stuff is done in addition to the engine itself being in good working order;
02 Sensors
MAF Sensor
Fuel Injectors
Ensure the boost hoses are all good
Replace the TCV/BCS
Reset/renew the actuator
Good thorough service