My 03 Regal had the SD headers hit the drivers side fan. It was actually resting on it. I let it go for 2 years and never really had an issue until I heard the fan cut in and out when I shut the car off. Pop the hood and look and there are sparks coming from the drivers side fan motor (where the header was hitting).
I ended up having to find a set of '98 fans from a Regal and they gave me an extra inch of clearance. Apparently the 01+ Regals had a larger fan/shroud.
first pic - Stock 03 Fans. 2nd - '98 Fans installed
