your right sir, Thank you very much for your help. I moved the chain round one link and now all is good in the world. It's only easy if you know the answerThey are narrow wide jockey wheels.
It looks like the wide part is sticking in the narrow sections of the chain.
They just need rotating by 1 tooth/link so they match up with the chain properly.
I still found them to be a little noisier than the stock SRAM wheels though.
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