I'm not sure about the exhaust system ... pretty sure it's stock, and my mechanic who helped me get it "road-worthy" made no comment on it, nor did he do any work. Given that it's fairly quiet *outside* at idle, I *think* it's OK, but I'll have to get back to ya on that one --- hopefully I can find someplace nice to get under it (no garage at home, yet).
As for modded, I don't *think* I am. I don't see any evidence, nothing was mentioned at time of sale, mechanic didn't say anything, etc. However, Rocketman, your description seems to be "spot on" with the effect I note.
I will add that it's not so noticeable if the load is easy, but against a headwind, for example, it can get downright annoying, as I said.
How would I know if the turbo is modded? Boost gauge never goes above about 11, so I think that'd indicate a stock turbo?
Thanks, gents!