Here's what I've done so far...(not in order)
replaced the radiator with an aluminum CX racing one (ebay special)
replaced TurboXS BOV with stock BPV - wasn't for me hated the backfire on shifting
cusco turbo heatshield, don't think it helps all that much but I got a deal on it and bling!
silicone between Cobb SF and TD04
CD/MP3 headunit (Kenwood?) and some pioneer speakers - they sound a good bit better than stock but not awesome enough to go into detail
installed sound deaden-ing material in front doors (doing back soon), used fatmat. its ok, it did cut down a good bit of noise
Logged, logged, and read some, logged, read more.. and tuned my ecu a little. It had a map that wasn't stock on it when I bought it. Didn't know anything about the tune that was on it, who did it what were they trying to do.... I'm OS tuning it now. Got it running ok, got some knock that I think is bogus but need to do a little more logging and looking, then I'll push it a little.
tinted the windows 35% front and rear - that sure did help in the SC heat
I made two things out of a sheet of aluminum for under the hood. A radiator shroud cover, that was easy, and an airbox, not so easy. The airbox didn't turn out exactly like I wanted it too but I'm sure it helps a little as it blocks some of the heat coming off the engine. When I go to remake one I'll make it a little taller so it can have a lid or something put on it and also find a way to move cool air into it, fan or route the under hood air diverter thing.
I also made a switch to make reading/flashing my ECU easier. When I get un-lazy I'm going to install it in one of the pre-drilled blanks near the cruize button...
A couple of weeks back I installed a Deatschwerks DW200 (255lph). --One tip, for noobs like me, on the install process is after everything is plugged in and dropped into the tank, bolt and cable everything up BUT the fuel delivery line running to the engine. Get a piece of vacuum tubing or whatnot and attach one end to the fuel delivery coming out of the take and run the other end into an empty container that can hold fuel. Secure the tube to the container, you don't want fuel spraying all in your backseat do ya? Turn the car to the "ON" position, no need to start it, just want to turn the pump on. Turn to "ON" once or twice just to make sure its pumping. You should hear the pump whir and spray in the container. That's called priming I believe.
--another side note, I put the DW sticker that came with the pump on top of the access cover for the fuel tank pump assembly, the piece in the trunk. I wrote the date I installed it on, on top of the sticker so if I ever loose my mind and sell/trade it dude won't have to dig in the tank to know what's in there.