Here is results from a C5 owner installing 1.8 rockers which we then PCM tuned and then same car with the stock 1.7 rockers also PCM tuned.

As seen and felt by the driver and passenger is the 1.8 ratio rockers lost in both horsepower and torque.

This again shows spending money on mods does not assure there is any gains and could cost performance.
Parts must be matched to assure they all are a positive overall for decent gains.

1.8 rocker results on the left - - - 1.7 ratio on right