I run a euro non cat m3 in my country. have been running the car on 98 oct leaded. new legislations are phasing out leaded gas - the last batch will be sold by the end of the year. Is there a substantial diff in engine design between the cat/non cat version of the e30 m3. am looking at switching to high oct unleaded and I will only use additives/ lead substitutes if I have to .... does anybody know if I can switch to unleaded gas without killing my valves?