Strange Pattern During Material Render

Hi All

I was going to ask for help with this but I've just worked out what was wrong and fixed it. Thought I'd post it here in case anyone else has the same problem.
I was trying to get some final "beauty" renders off my finished mesh from the Vehicle Modelling tutorial I've done. I noticed some weirdness on some pieces in the tail in the render.
[You must be registered and logged in to see this link.]

First thought was interior faces so I deleted a face at random and sure enough there was another face underneath.
[You must be registered and logged in to see this link.]

Experienced Blender users have likely already spotted the problem. The grey bar that's not highlighted is the giveaway. Its been created by a mirror modifier that is needed. But I also had the mirror modifier on the pieces in the middle which wasn't needed. I must have joined them together at some point.

Interestingly the engine parts which also have the problem was a slightly different problem. They had two mirror modifiers on them. I must have copied a piece that already had one then applied another later.

That's what you get for working into the early hours and or drinking while you model All sorted now.
[You must be registered and logged in to see this link.]

Lovely shots! It's good to see that all you need is a torx key to adjust the tail there.

Ha ha I hadn't thought of that. I think it's meant to be some sort of exhaust actually.

Thanks. I'll bung the final renders into a finished works thread.