Engine sound like it's knocking after fixing stuff after sitting

So my truck has a 5.4 Triton, it has been sitting for the last few months at least, ran perfectly fine when parked, we did a oil change before it got parked, and have been doing little odd and end maintenance on it, rear end work, front end work, wheel bearings, new tires, etc, well....as we have been bringing it back to life, well.... we just sealed up exhaust leaks, and now it is knocking. Never knocked before it got parked. now sounds like a bad knock in the motor on the driver side, checked to make sure the plugs over there where all good and tight. All good but still knocks pretty badly. Some help!