GMC Troubleshooting Questions? Ask a Mechanic for Answers
Fuel pressure spec is 55-62 psi. It sounds like you need a fuel pump.
No, rodents couldn't have chewed on anything that would REDUCE fuel pressure. If the pump is running, but you're simply not getting enough pressure, you need a pump.
You can borrow a fuel pressure gauge at no cost at place like Advance and Autozone.