I just bought a 84 supr celica and want to put some rather inexpensive mod together . I have read online about cutting circle in the airfilter box and putting a K and N filter in. Good or bad idea?? There are pictures of what i am talking about doing at www3.sympatico.ca/dean.anderson4/index.html :sunglasse

I assume you are referring to a open air filter mod. I know for the mk4 supra you can install a k&n FIPK to increase flow, which is similar to what your doing. It sounds like a good idea, but i would watch out and have backup cash incase you "cut" something wrong, lol. I would recommend the mod but even moreso i would say to look for an aftermarket intake for cheap. Good luck to you.

Will this mod hurt my MPG

if anything this will actually help you mpg because you are allowing your engine to breathe better. but the "fun sound" may make you want to gun it for about a week or so...trust me, intakes have that effect on everyone...just watch how hard you press the gas.