I tried the pedals and the G27 register a false clutch signal when I press the gas pedal. Do I need to wire the clutch pin with the ground wire?
That can happen when you leave an analog input "floating" with no input connected to an input wire.
The wire acts like an antenna and picks up signals and expanding/collapsing magnetic fields.
I grounded the clutch, problem solved!
That's one good way to fix it.

If the clutch is on the Z-axis, it may cause a runaway scrolling issue in some front ends.
The un-centered Z-axis (a.k.a. mouse scroll wheel) causes the MAMEUIFX menu (and probably many others) to constantly scroll.
You can avoid that issue by using a pot that isn't attached to a pedal
or two
*equal value* resistors to make a voltage divider that provides 2.5v on the clutch wiper wire to the encoder so the axis is always centered.
- 1/4W or 1/8W resistors between 2.5k and 50k will be perfect substitutes for pedal pots between 5k and 100k.
5v ---- resistor 1 ---- clutch wiper ---- resistor 2 ---- ground
Scott