912 run rough on climb or heavy load

First thanks everyone for taking the time to reply. So just a bit more info to cover off the vaporization. I have recreated over 2 different days and can replicate regularly on the ground but running the engine at 5000 (almost firewall) .. I have run with aux fuel pump on and no apparent changes. This engine ran perfectly smooth on the flight over and I fly very regularly (1 - 3 times a week).

Roger, I will try the carb sync but again I fly this plane all the time and have experienced my carbs being a bit out of sync and nothing like this level of 'shake'. No noticeable change in fuel pressure and no maintenance done recently.

To rule out electrical is it possible that one circuit failed maybe months ago and I would just not notice as I do run ups at 4k and mag drop every flight but I have never done mag drop in the air under heavy climb. Now the other module or coil has failed in a similar fashion? Just trying to get a sense of a direction as I don't want to throw good money in an incorrect direction.. lol.. Also as I have spent a considerable amount of time already checking everything fuel related and what I can check ignition related I thought maybe about 1. new fuel 2. maybe temporarily setup a primer that I can give it a small squirt when it breaks down to see if that cleans it up. I feel looking at the plugs that there is almost no chance it is a rich condition but rather a lean condition however *all 8* plugs look identical and on the white side.. 

*edit* sorry forgot to address the air leak comment. Visually the mainifolds still look brand new absolutely no discoloration around any gasket. The carb 'boots' look brand new as well no checking whatsoever. I have not gone further down that road. 

Might want to take notice of EGT temp differences when problem appears helping to narrow it down to one side of engine

Unfortunately I don't have EGT's but I agree I may need to install them. Not something I have needed much with a 4-stroke in my life but I get it.

Hi all

I would point out on the intake manifolds the pressure is below atmospheric unless the engine is fitted with a turbo.  Therefore a lean burn can occur with a leak without leaving a stain from fuel.  The air would bleed into the manifold, not out.  

Cheers

I would also check that the carburettor / throttle cables are moving together, without any tendency to "stick"😈