Anything I can do to make my car happy?

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Hey guys, I have a 1992 300E with 106k miles on it. My dad says that he took it through all the preventative maintenence as outlined in the little booklet. I, however, seriosly doubt that considering he is of the group that thinks you shouldn't even look at it unless its broken. My question is, is there anything in the way of chemicals <--sounds pretty bad that I could/should put in the car to clean out the injectors, purify the engine, whatever else you wanna call it...? I did a little reading, and ive heard some bad things about injector cleaners. I wasn't gonna put anything in in the firstplace, but then I thought that the engine is getting old, and I might as well see if there is anything I can use to clean it out so maybe I can get most of that 177hp kicking. Any suggestions? Comments? Warnings about engine cleaners? Thanks.