Did you check tank capacity? Dollar to donuts the tanks are different size.

Mrx4 tanks are a little undersized around 1-2cc when I tech'd them a while back as are old serpent white tanks. New tanks are oversized from serpent around 2-3cc

Perhaps the new car has tank that is 125cc now.

Being at exactly 125cc is REALLY important when running 5 minutes.

I had old tank in my car and could not make time at last race...beat my head against wall and tech stated it was 2-3cc under after final! My old tank was oversized and I did not want to hassle with getting to 125cc so I just ran tank that I thought was 125cc...my mistake..lesson learned...always check.

Perfect preparation prevents poor performance. Best tuning tool I found to date.