So long term I plan on building a beast but quick intro bought a 08 csrt4 a month ago with 150k on it. Right now I'm just doing standard maintenance. I wanna know what the best of everything is to go with. And also what's the quickest way to spit flame.
Do whatever is required for 100,000 mile service.
Then do a leak down test, compression test and send your oil out for analyst.
If the sample comes back without mass amount of metal particles, low compression in a cylinder or blowby from the leak down test, then you are free to mod.
As for what to do. Start with either a Diablosport Intune/Predator which I think is a the better option. However it depends on what you want to do. It seems to me you are more about noise and making a spectacle out of yourself. To get flames shooting from the exhaust you need to delete the cat converter and any muffler/resonators in the exhaust.
If you don't think you'll be doing much, get the Real Tune MSK1 for whatever fuel is available in your area. That is an easy 50+ hp gain on 93 octane and it's a safe tune.
That said you'll make more power with E85 and a custom tune either from a Diablosport CMR or somebody familiar with the platform that uses HP Tuners, the Caliber is supported on both.
MSK1 will be about 310-320 hp otherwise stock car, Ethanol will make more power everywhere at the expense of more frequent oil changes and 20% drop in fuel economy.
If you plan on adding a wastegate, downpipe, upgrade the intercooler, etc; While MSK1 adjust well to these changes it's not perfect and you'll be leaving some power on the table. A custom CMR tune (Diablosport) or HP Tuners will get the most out of your upgrades plus you'll be able to program Boost By Gear and upgrade your injectors with a rescale.