Just yesterday I had 30 km left of E70 left in tank , & I changed to my 98 tune , Now I did this prior of going to the servo to get fuel which is just 10 minutes from my place , When the loaded file was finished I turned car on & it would not idle , finally car idled for a while to make to BP servo to fill up , now the car every now & then car drops revs & stalls at lights , why is this happening??