I think they are more durable than people give them credit for. I run a diesel business and I just tore down my 4d55 to rebuild it and the rods are pretty stout for that little thing. The only drawback is running that much boost with 21.1 compression, you risk popping headgaskets. I am lowing my compression a little and torqueing the bolts down a little tighter and that should allow me to run more boost.

1991 ford ranger ext. cab 4x4 with a mitsu 4d55 and 5 speed tranny

2000 dodge ram sled pulling truck with lots o power and allison auto tranny

All built by me Stallion High Performance 419-545-4217