Hi, the motor change suggested was for 480 motors with a nominal 7.2v rating.
The motors you have fitted if my memory is correct( it gets worse just lately) lol,
We're MFA 500 rated with 4.5-15v, as you had car esc,s fitted I don't think you
Could run at more than 7.2v with them. With the 6v-12v nominal rating your
Rpm will be 7500-15800 so on 7.2v you will be on low revs even when flat out.
No doubt I will be corrected if I am wrong, there are some very clever people
On this site who know a lot more about running gear than me.
John