I came across this on a Audi forum.
http://www.audiforums.com/m_693578/mpage_1/key_/tm.htm
Here's the text from the post:

"Hey guys, I've got a 98 1.8T. I've had a k04 and chip for a while and wanted to get more performance. I was recommended to port and polish the intake and exhaust. We found out they used abrasive material to do it like gritty sand. So I got with my friend that tunes Hondas and we decided to try it ourselves. We got a bag of sandblasting sand and hooked up into the intake and started the car. We had to hold the gas so it would run. He wanted to let the engine suck in the sand through the intake so it would port it out and then push it out the ehxaust so it would port the exhaust manifold.
I was worried that it might cause problems but he figured it'd be OK as long as we didn't make boost and it get sucked in the turbo. After running the car and letting it suck in sand we got about half way through a 25 lb bag. The check engine light was on and the engine was bucking and kicking and sounding really weird. We stopped and hooked the car back up normal and took off the sand supply. We tried to start it again and it was really hard. Once started it couldn't idle and kept making weird noises. We took it out and drove it and it started to make scraping and knocking noises.
Help! Can anyone tell me what to do! My buddy only does Hondas so he doesn't know much about Audis."