The injector o-rings looked okay when I inspected them. I sprayed the nozzle out pretty good with brake cleaner and shot a good amount of fuel out the spider and line. The injector is clean.

Cylinder #3 acts normal at idle and run up. At full takeoff power the engine stumbles as #3 goes cold. 

I've already done a visual inspection of all the clamps and couplings and conducted a soapy water soapy water test of the intake system.

There is a definite correlation between RPM and #3 going cold. Under about 2450 rpm ROP, #3 was smooth but a good 70 degrees colder than usual. When switching to LOP, #3 CHT comes right up in line with the other cylinders as normal and I can increase the rpm. When #3 get's rough, egt drops lock a rock. 

I tried using the high pressure fuel boost and modulating the flow with the mixture for a full rich condition but #3 stayed pretty cold. 

Mags checked out in all phases ROP and LOP. 

The #3 valves looked good with the scope and the compression was 72/80. The top plug looked a bit oily when I pulled it.