1999Tacoma runs fine but seems a little tired.

My 1999 Tacoma v6 4.3L runs fine but seems to be getting a little tired. I only have 115K miles on it but I seem to be losing a little "get up and go". She starts and runs fine but seems to have lost the "push you back into the seat acceleration". I'm in Denver at 5280 feet but I don't think that should be a any problem. Would new plugs be a solution?. Thanks for any advice.

 

my 2004 seems the same at 246k miles but sometimes I think it may be all in my head I think,or needs a oil change,i changed out a dirty air filter today but still feels tired