A shop told me that the STi mounts actually lower the engine slightly. Not sure if that's true or not but it could make the problem worse.
I'm also running the A350 and have the STi mounts sitting on the shelf. I had to hammer the engine cover in a few spots to stop the runners buzzing on it.
It is really unfortunate that the headers seem to have a number of design flaws despite the price point and performance advantages. I've had a bunch of issues with the 4-2 OP flange bolts coming loose and disconnecting on track. And although it seems not everyone has the issue—which already raises eyebrows in my book—the requirement to basically destroy your engine cover to make them fit seems a bit silly.
If they weren't so awesome I'd have chucked them long ago
