Having any tint on the front windows used to be illegal here in Illinois, but a few years ago they changed it so you can have 35% on the front windows. The windows on both our Vibes are tinted 35% all around. The windows on mine (the silver one in my signature picture below) were tinted before the law changed and I never got bothered. I have actually never been pulled over for anything in the Vibe

.
I don't know of any direct-fit aftermarket rear strut bars, but
TRD makes one that will fit the GT. I installed the TRD front strut brace on both our Vibes last summer. The difference it provides is well worth the cost. It is about half the weight of the stock one, it looks way better than the stock one and it is one solid piece so you can actually feel it holding the front end together much better when turning, etc.
We have DDM Tuning 35w 4300k HID bulbs in the low beams (#9006)of both our Vibes. Again, something I highly recommend. Just make sure you aim the headlights down a bit after installing the bulbs. As far HIDs in the fog lights go, I have not had much success. They flicker when turned on for some reason. I am considering ordering wiring harnesses, but don't know whether I want to spend any more money. For the time being, both Vibes have Nokya hyper yellow Stage 1 bulbs (#9145 / H10) in the fog lights which provide a nice yellow color when lit. I actually installed Headlight Armor yellow fog light overlays earlier this year, but ended up removing them after a while because I got tired of the look of them. Very high quality product though if you decide to go with overlays.
Both our Vibes also have
v-LEDs 5000k LED bulbs in the license plate lights (#194), reverse lights (#921) and all interior lights (if you have a sunroof, the map lights are #194 and the center and rear overhead lights are #DE3175 / 31mm). They are super bright and very high quality.
As far as intakes go, I highly recommend the
K&N Typhoon. Many owners here have it and both our Vibes have it as well. Not a single problem with it over the almost 5 years it's been installed on my Vibe. Our setups are finished off with AEM Brute Force Dryflow air filters (#21-203BF) and AEM air filter wraps (#1-4000) [to help keep dirt, bugs, etc. out of the filter]. This intake provides a nice engine sound when accelerating without being too loud and obnoxious like an aftermarket exhaust can be. I have no desire to get an exhaust on either Vibe because this intake provides a great sound while not being too loud.
Check out our Garage threads (linked in my signature below) to see pictures of all the above parts installed. Let me know if you have any questions or anything. I look forward to seeing more progress from you and your Vibe

!