Is it normal for a 225 to...

Nope. I don't notice anything, infact I think it idles better than after it came back "tuned to perfection"

Not idling....but give it gas while in Neutral and get the rpms up.

If you can rev up the engine in Neutral without the noise and the noise is only made while the car is in gear, it seems to me it's not coming from the engine itself but rather somewhere rear of the engine.