Car runs sluggish and 21MPG performance :(

[yami]

I have a Mazda Protege, 1999, Automatic Transmission. It is in really good condition. A few month ago I purchased it used, it had 3 previous owners and CarFax showed it was well maintained by the first owner who had it for almost 8 years. Last two owners, I have no clue.
Afetr buying it, I changed its Timing Belt for the first time in 123500 Miles. Everything is fine but the car is Sluggish and "it feels" like I am driving it with hand brake half on. Initial acceleration is good (especially without any other passengers) but after few seconds the transmission shifts up, I miss acceleration and it runs like a very old car. Also gas mileage is 21 MPG (for City/Hwy mix) which I think is not good. Wonderfully its MPG drops a little bit in all Highway trips! Air Filter is good too.
Despite I know my car is old but still I want to fix this problem. People say it would be due to Tuning or Front Wheels Alignment or Injection Computer failure but these are just guesses. Thanks for any advice.

ps. I posted this to few Protege clubs, I hope it is not against forum policy.

[libertine1975]

I have had the samw problem since changing my timing belt on my 1995 323 glx. I was told that it was the MAF (mass air flow sensor) that had packed up and that is a costly replacement. However, after further checking a mechanic friend said that it was due to the timing belt being off half a tooth or so, Top Dead Centre off. I took off the belt and re-alligned the crankshaft tdc with the cam shaft timing marks. Took me a while to sort and as soon as I started it noticed the difference as was on high rev;s for 10 secs or so before levelling off. Spot on ever since, hope this helps.....