Truck has 211,000 miles. Engine is louder when I drive it especially when I give it gas.Should I use high mileage synthetic oil.No leaks.

To a certain point, I agree with Tom's answer. Is it exhaust or engine noise? As far as oil is concerned, I use a 50/50 blend of synthetic/regular oil in my Dakota with nearly 150k on it. It has worked quite well, I even use the blended in my wife's 2009 Toyota Camry.

What I hear is engine noise. Engine get louder when I slow down and then give it gas or when I completely stop like at a red light then press on the gas. Like I am pressing to hard on the gas. I just read that changing to another oil was not be good for my truck after all these miles.

If it sounds kinda like a jet engine turbine, it could be your fan clutch has gone out which costs about $50 to replace if you put it on. If you have a mechanic you trust, I would ask him to take the truck out for a run around the block and give you his opinion. Also ask him his opinion about the synthetic blend. Mine suggested that I move over to the blend when I hit 100k miles.