No they claim that you don't lose any power on PETROL with it installed. That is it doesnt restrict airflow to the carb like some do. I could still have my nice K&N on top :-) As for the aircon, most people would rather take their shirt off in summer and look like a bogan than sit in air-conditioned comfort, those bloody air cons zap power you know, even when switched off you are still turning the belt. A lot of people think air con is for poofs or something. I pride myself in haveing a comfortable older luxury car that is as pleasnt to drive as a new one. ie; auto/air/steer, electric windows and seats, remote central locking, LPG economy if I want it and retro style (real chrome) that you can't buy on a car of today at any price.