My understanding, having owned two TDI vehicles affected by the recall, is that the statement of not affecting performance and fuel economy is based on the fact the EPA numbers were calculated with all the emissions systems active.

Now what will be affected are all those individual reports of ten to twenty percent better than EPA numbers many TDI fans love to rave about. Both my TDIs were like 40 highway / 30 city rated and yet over their lifetime the vehicle average was closer to if not higher than the highway number. Granted I do not drive like most people I see; racing to each stop and such. Still the numbers I had versus what the EPA said cannot all be explained by good driving.

My question is, if it was so easy to slip diesels past emissions testing then how about gasoline powered cars? Worse with the regards to diesels I think a truck manufacturer was caught cooking numbers in the nineties?