Tested my S4 on the runway at RAF Brize Norton Sunday as I had a few runs left and it was raining so I couldn't run my Caterham. S4's performance was frankly dissapointing. Its got a QST 310bhp chip plus a Miltek and it managed 14.2 over the quarter which is OK I suppose except the engine ruins out of boost at around 4000rpm and sounds all harsh and thrashy. Same problem effected top end where it only pulled 142mph (GPS - Speedo read 151) over 1.5 miles. It makes a great tow car pulling the & on a Brian James A series (aboutr 1 tonne all up)with relative ease and achieving 22mpg at a constanmt 70mph cruise. What do others get in terms of qtr mile times? I rather expected to be getting at least 160mph on the runway.