2003 4Runner, Noisy valves & Possible more

I have a 2k3 4Runner with the V6. The engine runs with clicking valves that don't bother me that much at idle. Even when I rev the engine up while parked it sounds fine. When I'm driving it is a different story. When driving next to a wall or sound reflector of some sort the car sounds bad. It sounds like possible exaust leak which just amplifies the clicking valve(s). When the car is parked and running I cannot reproduce the sound. I've even tried holding something over the tailpipe while it is running to find the leak but to no availe. The 4runner operates without a check engine light, gas mileage has remained consistent, no abnormal discharge from the exause, no foamy oil, no loss of fluids (coolant, oil) and no loss of power.

Please help, just looking for some quality advice before folding and driving it to the dealer.