around town mpg is about 21 but on the motorway you looking on average 28-30mph. Petrol to fill on V max or BP Ultimate for a tank £65 which the Z prefers to drink but can drink the non alcholic bog standard unleaded.
No major nasties to report. Yes a very few have had a gearbox replaced under warranty. The problem was solved. The biggest wear and tear is tyres with the fun of rear wheel drive :teeth
Service cost aren't major. Max you will pay is around £270 for a big service down to £150 for a little one.
Inusrance, is impossible to quite on with so many conditions effecting price. Best advice is to give some companies a ring. Some people pay over a grand and then some pay around £400
ECU cancels any performance mod gains although a larger plenum or plenum spacer is a good one to start and with noticable gains. Of course there are many exhaust that have a wow factor. Forced induction is another matter starting from around 6k
Just get a test drive sorted and you'll see if's well worth every penny