Cleaning inlet manifolds

Does anyone ever clean the inside of the inlet manifold?
I do this every 10k miles or so, or on a tear down.
I don’t know if this is common knowledge but there’s about 2bhp pretty much across the engine rev range by about 3 hours work on both sets of inlet manifolds with particular attention to pots 1 and 4...
They are the tracts that are always in worst condition suggesting velocity is down. This would lend itself to a less than ideal tract shape so it’s worth getting the dremel out and blending some of the casting back.
Remember, leave it coarse on the inside of a bend and polish on the outside - helps it all along

You seem very knowledgeable about this stuff so I will ask you (and others!) about cylinder wear and tear:-
If modern cars (e.g. the new Fiesta 2018) can disable on the fly certain cylinders then surely this will abnormally and quickly wear down these cylinders, ultimately rendering the engine useless but with less worn cylinders? Then what is the point (other than "fuel" savings)? Or does the engine cycle through the cylinders thus averaging out the extra wear?

But surely although the cylinders are "disabled" they are still being lubricated as normal along with the others

I don't know how the disabling method, but would it only ever disable the same cylinder ?

on a 4 cyl. would a simple sequence (forgetting 1-3-4-2 or 1-2-4-3) be: 1,2,3,4,- 2,3 4,1, - 3,4,1,2 - 4,1,2,3, then repeat, 1,2,3,4, et al.

So in 10 revolutions, instead of 20 firing cylinders, only 16 ?

You seem to forget that disabling any of cylinders whith it self brings keeping the valves open to reduce the compression work. It is not a matter of simply shutting down an injector as you would still have all the losses in the engine and have to make the remaining cylinders work harder

I do appreciate that the valves need to be open, or you would still have a compression stroke, but do you know if it is always the same cylinder that is disabled ?

And how about engine braking when the throttle is closed ? I know that the fuel is normally cut off on all cylinders on the over-run down to about 1000rpm on a lot of cars, but with cylinder disabled, the valves would need to operate normally to provide engine braking ??

I'm going to have to do some reading !!