In good air, with the standard clothe interior w/o passenger seat or rear seat, I'd expect I could see 11.7s in good air where I am (Mid-Atlantic). Bone stock, with the full leather interior upgrade and my 200 lbs in it, my car's squeaked into the 11.8s on one pass and 11.9s on a couple early in the year. Basically, it's a 12.0 car with potential to go a bit quicker or a bit slower depending on the weather / track location / etc.
The only mods I've done are a drop-in K&N filter (which I haven't proved to be an improvement or not) and I picked up some discontinued Race Star Recluse wheels so I can run Mickey Thompson ET Street Front 28-6.00x18 and ET Street S/S 305/40R18 tires the days I drive to the track. The standard Nexen 275/40R20 drag radials worked OK when new and on a well-prepped track. However, they'll get sketchy well before the tread's worn out and any short-sidewall tire is going to have trouble hooking consistently on less-than-perfect starting lines.
The car isn't necessarily faster w/ the MT tires & wheels combo, but it's much more predictable getting off the line. The OEM Nexens would either stick, or they'd hop & spin. My last track day was Saturday and the purpose was to see where I need to set the rear tire pressure w/ the MTs to get a more consistent 60-ft. The lighter front tires & wheels may add a touch of MPH, but the rear tire & wheel setup is also heavier than stock. I'm running less air pressure in the rears now, which may scrub off some MPH. However, if the car won't hook consistently, it doesn't matter to me if it's faster on the passes that it does hook.
I don't know of any cheap "bolt-on" mods for these cars to increase engine performance. And that's not really my intent, either. This is my daily driver that allows me to go have fun at the track while I'm still trying to pull a miracle outta my a$$ and get my '73 Challenger back to the track. Here's a snapshot of all my full 1/4 mile passes, meaning it doesn't include any pass where it simply blew off the tires or the 1/8th mile bracket event I raced a couple weeks ago.