2006 Kia Optima tuneup/loss of pep

basically two separate issues possibly tied together. The last month or so the car has seemed to lose its pep, I changed plugs (went to Bosch platinum 2), coilpack/plug wires seemed ok, changed air filter, changed oil I use the best Amsoil and filter, two tanks of good quality injector cleaner with high test gas. the vehicle is not running bad just not peppy. took a trip recently lots of power at high speeds, pretty doggy in the mountains though at times had a hard time maintaining speed.
Is there more to a good tuneup??? to get back that peppy pulling power, and shouldn't the computer have compensated for the higher elevations during our trip???

would cleaning throttle body and MAF help?

I'm old school and used to old engines, thanks
Surgery has me broke or I'd upgrade the question.