Codes 120308 and 118001?

I have been struggling alone for 1 year to fix these codes. II had an engine change. I have resolved 120308 Charge air pressure too low by sealing all the connections making them air tight. I didn't change the seals but applied gasket maker everywhere which sealed everything, like intercooler pipe intake air, throttle seal area, breather pipe. But I am still getting 118001 fuel air mixture too lean. I get code 120308 off and on and also sometimes while taking turn my transmission malfunction kicks in. Very confused, please advise.