Aside from plugs, MAP sensor, tune, and possibly intake...what is there to do? Hardpipes worth it? Been having a tough time finding a source for parts.
Depends how crazy you want to go. The standard 3 are the plugs, MAP sensor, and tune. Beyond that there is colder thermostat, down pipes, cat deletes, and meth injection, as the other "common" mods. Intakes seem to be pretty worthless other than making cool sounds. I've yet to see anyone claim any real difference from an intake.
The tune, MAP sensor, and plugs really make the car feel like a completely different car. I'm not going any further than these, because if anything does ever go wrong, I'd like to be able to turn my car back to stock in 15 minutes, instead of having to get under the car. I decided I'll take my chances with a warranty claim if something goes wrong. If Ford sends out an engineer and they find that I tuned it...oh well.
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Ecoboost Performance Forum Most guys have Taurus SHO's on there, but a handful of Flex, Explorer, and MKS drivers too. Regardless, modding is all the same on the Flex/Taurus/MKS/Explorer.
You can buy a tune direct from LMS or Unleashed. Buy the MAP sensor from Rockauto.com (much cheaper than other places), and you can buy the plugs from Amazon.