Reduced engine power light

I have to ask, how long since a tune-up? Are there any applicable trouble codes? To check codes, yourself, at the least, you need an obd2 code reader that will check manufacturer specific codes as well as po codes.
As far as the throttle position sensor, you can check ref voltage--ground and signal using a digital multimeter. With key on, hopefully, you can get on the signal wire, move throttle lever up and down/open and closed, see if voltage signal moves smoothly. If it does, I don't think that sensor is the problem. I haven't looked at the wiring diagram for that sensor?

The maf sensor seems to be a common issue.

At the top of page is a link for "repair guides", take a look if you have time, some interesting info.

Just to add to this one if the reduced performance light is on there is most likely a issue with your throttle body assembly and the connector going to the throttle body. Very common I have replaced tons when I worked at the Saturn dealer. If you have a hard shift into all the gears then most likely you need to replace your line pressure actuator in the transmission. That is a really common problem as well. Post the exact code numbers not code descriptions and I can tell you more.