Reading wrong MPH?
 

i noticed when im doing lets say about 70mph on the gauge, my commander would says im doing 106 which is about 65mph. i noticed it is never acurate, is my gauge going bad, of the pfc suppose to read a little off?

im sure the commander is displaying speed in km/h

he said that smart guy...

the pfc should be accurate. i wouldnt trusts your speedo. its common to see 5mph differences, but not till you reach really high speeds.

The stock speedo is fairly accurate when it's working, especially at cruising speeds.

What size rim/tires are you running? I believe if you're rolling on greater than a total 26" wheel diameter, then it will make your speedo read low. Check out sucklab's chart in the tire/rims section.

https://www.rx7club.com/suspension-wheels-tires-brakes-20/fd-wheel-tire-sizing-416251/

my speedo reads high, 5-7mph faster then Im going at 70

sorry, i fail at reading comprehension sometimes

i have 17' rev rims got them with the car and never really looked into how wide they are (not that wide)

its no prob...sorry for being such a smart ass

Get a GPS and independently verify what the correct speed is.

Check on Tire Rack or other some other tire site to compare your tires' revs/mile to the revs/mile for the stock 225/50-16 size. If they are different, that may be the reason.