Thanks for replying.

Rowhard code 13 was read by sticking a wire into port 8 and counting the flashes on the check light. It does indeed mean shorted ground but we followed the instructions we were given to find it and drew a blank. Have you any ideas where we should look? The check light is constantly flashing and the speedo always jumps around when you get above 70 mph. The idle when started from cold is fine but once the car warms up it drops.

Ruflyf we have checked the 22mm bolt and that is really tight so it's not that but I will try and check the pipes that you suggested.