never checked the high side ,,when kc was installed reinstall the same 134 that came out.
(recover ac system) and it would get cold for the first 10 or so minutes, so i had a few cans of 134 , so i added one VERY SLOWLY psi was going up around 80 to 90 ,,,backed off went slow ,got the can in and the psi was holding around 50 psi been good for 2 years now. remember i have no,,,NO heat exchangers, when i first installed my KC i used a H E , could only get the iat's slightly below ambient, but would not stay there,, removed the HE,,now good,,
you might try with the 12a ,,,low side about 50 to 60. they will equal each other , when turned off anyway.
you have added hose so u need more freon ,,going up 10 psi just let the both (car $ KC work) jim