flush combustion side of heat exchanger for Dunkirk/Utica 95M-200

cas1717

I have a Utica UB95m-200 .This model is also sold as Dunkirk Q95-200. Made by ECR International.

The heat exchanger is sealed cast aluminum and same as in the Q90 125-200 boiler.

The manual from ECR says "Aluminum oxide deposits may be
rinsed away by inserting a hose into the burner opening of
the casting and slowly running water through the flue side
of the boiler and out the condensate drain"

I plan to do the flush myself as I already know the consequences of not doing the cleanup.
My HX was replaced in 2022 under warranty because the exhaust developed a hole from corrosion due to acidic aluminum oxide that builds inside the combustion chamber.
Could not find a contractor in my area (South Connecticut) to flush the aluminum HX. I did hire for annual maintenance but they brushed the igniter and run combustion analysis and checked for leaks, blockages, etc.

Hoping to find on this site somebody who's done the combustion flush on the Q95 or the Q90 model .
I'd appreciate any hands-on practical advice beside what's in the manual.
- if they used any chemicals . Like the Axiom F9-AL.
- is it ok to connect a shop vacuum to the drain
- how to check that no water is left in the combustion chamber (w/out taking apart the rubber gasket connecting the HX to the exhaust assembly).
-anything else to look for