00 altima gained power for some reason...

i noticed after revving high (its a manual) in 3rd gear that my 00 altama seemed to gain power and run better. problem is the check engine light came on. its done this once before and i noticed after using "recirculate" button for the heat (which i never do) it stopped and the engine light went off. well, i have to get my car (http://www.nissanforums.com/#) inspected and i know i wont pass with that light on. has this happened to anyone else? what was the cause/fix?

My 2000 nissan altima temp gage moves back and foreward but it do not go all the way to hot ti stays half way between hot and cold

my 2000 nissan altima temp gauge moves it never goes to hot only moves back and fourth betveen hot and cold