Ok, so I have been gifted this little Cobalt from my parents, and we have had it for 4-5 years before it was given to me, and it used to get 21.3 mpg avg., I , know I may rant a little bit here, but just bear with me guys, this is my first thread here. Anyways, back around the fall of 2014, I started noticing her lacking in performance, and at the time the avg. mpg was around 19.8, and that summer, my dumb little cousin had stuck a water hose up the exhaust and turned it on, didn't notice it until it was too late..... and I usually am just a back and forth city driver, the thing only has 41,000 or so miles on it now, and the avg mph and the avg. mpg are considerably low for what I should have, my avg. mph is 17, it never has hit over 20 mph avg, and the avg mpg now is 18.2 and I can never get it back up! It does lack in performance, and that's something I like to have in a car! I timed 0-60 in about 10.2-10.5 sec., and it should be doing it in about 8.5-8.7, it's the 4 speed auto anyway, but I notice a HUGE sulfur smell from the car after it sits for a while and I start it, I usually drive a GMC Sonoma 2.2, and my Cobalt sits in the garage for days at a time. I don't like to put that many miles on it, and it used to be a peppy little performer! I like the car and would like more performance and mpg from it as well. I guessed the lack in performance and the sulfur smell I get at idle after starting it back up after a few days is a problem in the exhaust system, maybe a clogged cat or something else, I don't know! Never has thrown any codes and I use 87 octane pump gas, $2.69/gal. from Sheetz. I would like to fix whatever the problem is so I can spend less on gas!