[spuntyb]

Have them done by a reputable dealer/shop, make sure the work is done professionally, and you will see little impact.

If you're talking about swapping in an LSx engine, and putting on some smokestacks, then maybe you're on to something, but otherwise I've not seen huge losses of value with well-executed mods/upgrades.

As I've said before in other threads, when I took delivery, my SA even suggested some upgrades, including forged wheels, a JB4 or similar tune, exhaust mods, etc., and this was for a lease. He reiterated the same to me: if they are done well, no need to worry.