Very good Andy, as you say I did open my self up for that comment/reply.

I was actually being serious, how can you convince your customer to payout £100 for this service when a bottle of forte diesel treatment or advanced fuel injection system cleaner for around £12 is advertised as doing a very similar task.

Not only that you can buy various different sprays such as egr cleaner, intake cleaner etc and one of which I used from forte (free as a test) and it actually did make a difference to the car although never completely cured it.