red pony

What I want is anyones opinion on the concept of re-configuring the performance within the pcm [the cars computer] to gain HP/TORQUE etc. My question ; Is the 'aftermarket' tuners better for the car in the aspect of durability/ longevity of the engine vs. Ford performance's computer up-tune? the reason I bring this up is that I bought a Ford Motorsports catalogue and in it, there was a statement that some aftermarket tuners may give you more performance by turning off certain 'safety' overrides pertaining to catalytic converter temp. limited max temp. at the expence of exaust valve longevity[meaning catastrophic engine damage] . Their claim is their tuner program doesn't touch those aspects so as to give you performance and durability. Has anyone got some feed-back to either prove or dis-prove this claim? I may in the future get my GTCS re-tuned. Inquiring minds need to know!