Highway use, the Solara gets (i think) very good gas mileage. My recent trip from Rochester NY to Atlanta, only filled up $65-$75 each way - thats it. Very very good on highway.
City wise - ah man... it guzzles as much gas as my mothers SUV. If i drive aggressively, it drinks like its a porche or something.
regarding the CAI. When I was about 16, I bought the CAi off of ebay. Made my engine rattle and shake after three days of having it in. come to find out, the diameter is too big and too much air was going in or not enough pressure. ANY CAI for the 2.2 liter solara, no worky really, unless your boosted.