For what its worth, I get:

[TABLE="width: 585, align: left"]
[TR]
[TD]Engine
[/TD]
[TD]APC Propeller
[/TD]
[TD]Engine Speed
[/TD]
[TD]Propeller Weight
[/TD]
[/TR]
[TR]
[TD]170 CDi
[/TD]
[TD]18.1 x 11
[/TD]
[TD]7850
[/TD]
[TD]132g
[/TD]
[/TR]
[TR]
[TD]170 CDi
[/TD]
[TD]19 x 11
[/TD]
[TD]7460
[/TD]
[TD]135g
[/TD]
[/TR]
[TR]
[TD]175 CDi
[/TD]
[TD]18.1 x 11
[/TD]
[TD]8160
[/TD]
[TD]132g
[/TD]
[/TR]
[TR]
[TD]175 CDi
[/TD]
[TD]19 x 11
[/TD]
[TD]7740
[/TD]
[TD]135g
[/TD]
[/TR]
[TR]
[TD]175 CDi
[/TD]
[TD]20 x 10.5 PN
[/TD]
[TD]7500
[/TD]
[TD]158g
[/TD]
[/TR]
[TR]
[TD]175 CDi
[/TD]
[TD]20.5 x 10 PN
[/TD]
[TD]7230
[/TD]
[TD]171g
[/TD]
[/TR]
[TR]
[TD]175 CDi
[/TD]
[TD]21 x 10
[/TD]
[TD]6700
[/TD]
[TD]171g
[/TD]
[/TR]
[/TABLE]













on Optifuel 30% ULV fuel. The 175 figures were with a proto engine and I've noticed the production engines are slightly below this in performance (~200 rpm).

From my experience the assemblies that affect the power include:

Head, valve fit
Pump
Piston / ring / liner
Rear disc valve

Assuming the engine used to run ok and it isn't about to destroy its main bearing, then the CAM gear should still be in the right position, but worth checking according to the instructions. I think you should double check the fuel residue you are seeing. If it is neat fuel mixed in with whatever to make it look burnt, it might be simply a pump gasket leaking fuel at high pressure. The disc valve is a common issue and can lead to significant power loss. If the valves are carboned up then unless you know how to re-grind them a new head assembly might be needed. Sadly the only real way to check is to part swap against new or known components.

Please let us know how you get on with this.

Best wishes

Keith