Falco, if you get a hole saw by any of the mainstream manufactures like DeWalt, Milwaukee, Lenox etc. you should be fine. I used a Dewalt one when I drilled the hole in my stainless steel turbo to IC pipe. The key is to use LOTS of cutting oil and slow speed. If you have never used a hole saw before, you would think it will never cut through metal because the teeth are so big. But, it worked great on mine and I didn't destroy the saw in the process. One other tip if you opt to do it yourself. If you clamp the pipe in a vise to hold it, don't tighten it any tighter than is necessary to hold it in place. Because if you over tighten it you will "ovalize" the tube and it will bind the saw as it tries to cut. HTH's somemore.
Mike Campbell