Regarding customer service, when I first e-mailed Justin to place my order, I didn't get a response. Mailed him again a week later and this time I got a response within about 2 days. But, once the parts were in my truck and we ran in to problems, I e-mailed him again and this time I had a response within about 15 minutes. So, ordering the parts can be a little tricky sometimes, but if you have a problem he'll respond ASAP.
As far as the parts themselves, so far I'm loving my IP and injectors. I've got maybe 15k miles on them and no problems at all, for an NA truck it's way faster than it should be. The only problem we did have was after the pump was installed, the truck just absolutely refused to start. Even giving it half a can of ether couldn't get the damn thing to start. Lucky for me though,
@towcat was the one doing the installation, he's got a big bag of tricks and he was able to get it going. If you're not going to do the install yourself, do yourself a HUGE favor and take it to someone like him who knows these engines inside and out, not just any old diesel shop.
One thing to note though, if you're running NA, turn the fuel screw down before installing the IP. Justin told me my pump was calibrated for NA engines, but this thing puts out more smoke than a flaming Iraqi oil well. It's a good thing I don't have a pyro