Alot of time, the transmission shift too soon so the car feels sluggish. You must verify that your transmission is in good working order... it stays in gear for good moment before shifting to the next... not a rapid succession as in 1-2 seconds to the next.
If the tranny is verified to be good, then you can do a minor adjustment to the tranny... on the engine where your throttle cable is, find the second cable that goes to the transmission... first one is actually throttle cable.
Once you find that transmission cable, turn the knob adjustment to take up the slack and shorten the cable. Everytime you adjust it, go for a test drive and with moderate acceleration, you should see that the tranmission hold in gear longer to higher km/h (MPH) before shifting. Adjust so that it feels peppy enough for you.
You don't want the engine to rev too high or on local driving, you feel the engine is revving too high. If you feel no change in speed vs shifting, then there is definitely something wrong with your tranny.
Otherwise, easy way to get some pep is shift from D to 3 when you want more power. Don't forget to shift back to D when satisfied. That's why D and 3 has no cog like other gears... for those moment use.