Whats your favourite Upgrade?

Not a power adder but my first and favorite mod is always exhaust.

Also not a power adder, but hands down my favorite modification so far is my blow off valve. every time you take your foot off the gas, you get that iconic PSSSSSSSSST sound and it still never fails to put a smile on my face, and it turns heads. its loud and fun and seperates your car from a crowd while driving. its all about smiles per gallon.

The Pedal Commander Throttle Response Controller. Takes away the lag off the line and just makes ur car a little quicker. No HP addition, it's just quickness. Also, if you can, paint the calipers. It's a badass look and it's cheap as a DIY. Especially if you have black rims. Throw some red or gold on the brake calipers...mmmmm. Hope this helped

This thread seems like a logical place to comment...

The last time I was in Mustang World (2007), the logical first mod was a high-octane tune and a CAI. However, on the Ecoboost, the consensus seems to be that Ford has already given us a 93-octane tune that automatically steps back on 87-octane if knock is detected. Anyone have any real-world experience on an aftermarket tune and CAI?

I just put a C&L CAI on my wifes 2015. Sounds like a shop vac when the hoods open which is awesome and it has significantly better throttle response. Not alot of hp gain but its quicker. If doing upgrades on steps this should be the first IMO. I'm not a gearhead by any means and i put it on in under an hour. Hope this helps.