Hi Bryan.
Thank you for posting on the forum.
When the image appears dull on the projector, and testing another lamp inside to ensure that the fault is not with the lamp and cleaning the filters, this is related to internal issues on the projector which require an optical clean to resolve the issue.
We have an article on our Knowledge Base which is explains how to get the best performance out of your projector. Please take a look at this link
I noticed that on your profile you are based in the UK. There is a Promethean authorized repair centre called TP Matrix. They will be able to give a price to clean the projector and inspect to see if any components are at fault also.
If you have any questions please do not hesitate to contact us directly and quote your reference number which is 00418908.
Adam
Promethean Technical Support