I've been doing it for over 20 years now with the drilling machine and never had any leaks. That tells me you are doing something wrong, maybe not enough grinding paste.
I know it can be done, but only few peaple have done it . It's easier to just get a shif box from Forced four, it's fully programmable, just like having standalone TCU.
For non believers Mahle are very strong pistons . This is mahle piston on Eagle rod after 50+ psi of boost pulls, all I had to change was the rods ( 300M this time ) the pistons where ok so I re used them & still are performing good @ 42 + psi street driven .
Looking at you log you do have a lean condition . The 14.1 afr that you see is afr est (target that the ecu is trying to get )car is not in closed loop .