Hi,
I'm not sure of the position of the pipe, but if there is no obvious reason such as, pipe too long/short, causing stress fractures. Then have a look to see that there is clearance once you close the bonnet. Also, if the pipe is "P" clipped on the chassis, get someone to rev the engine to see how much the engine moves in relation to the chassis. Constant movement will also cause stress fractures.
Cheers now
Ken Chapman
September 2007