I've got the service manual but it doesn't really state how many.

One thing I did find though was the firing order. The firing order is: 1-4-3-6-2-5 so this would suggest there are 6 of them right?

I have the service manual in .pdf format. It is 160MB and my web space is only 100MB so if someone can point me to a location to upload it to I would be more than happy to do this for you.