tx_zstang

Whichever is the best price for you for STAINLESS STEEL X or H. A shop will likely use aluminized steel and it'll rust out on you eventually, as can the welds. Know what materials are being used where, for long-lasting trouble-free exhaust.

An exhaust change does not need any tune changes. You won't "blow up" your motor with the factory tune unless you start doing things like nitrous or a blower. If you do things like add long-tube headers, you MIGHT need a tune change to prevent "Slow O2 sensor response" DTCs, but that's only to prevent those from coming up.

The tune is the car's computer program for operating things and making sure engine operation is safe and within limits. A poorly-written tune or one that is seeking every possible ounce of power and pushing the limits will eventually cause engine damage. Most reputable and experienced tuners will keep some safety margin in place to keep that from happening. The stock tune is very conservative, overly safe.

As such, a custom tune, from someone or some place that has experience with your particular car and setup, is the best way to get more performance out of the car. "Canned" tunes, those from the larger mail-order shops, are made for all cars like yours and are not optimal. Each car is unique and will have it's own specific operating and performance parameters that can be taken into account and used to develop a tune that is made specifically for it; that's the benefit of a custom tune over canned tunes.

These cars will automatically adjust themselves to varying conditions, as part of their tune. Slight variations are usually 'learned' and 'adapted to' without you needing to do anything. Exhaust is one such thing that'll get adjusted.
CAI's on the other hand significantly change the intake air flow characteristics and require (or are best utilized with) a tune change.

Hope that helps.