THEY NORMALY FLAME BEST ON OVER RUN.
I FITTED ONE TO A STENDARD SAF COS AND GOT NO FLAMES.
WHEN I MODDED IT TO STAGE 3 I GOT HUGE FLAMES.
IS YOUR CAR STANDERD? IF SO THEY WONT BE MUCH UN BURNT FUEL COMEING OUT OF THE EXHAUST AND THAT MEANS NO FLAME