Solved

Car performed unreasonable slow

Was hast du versucht zu tun?
Yesterday in our race my car was very slow. (https://igpmanager.com/race/live.php?id=64710807)

All of the grid did M start, I was the only one with S start.
My car design was well (all DP reasonable spent), my driver had full health and car was repaired

Was ist stattdessen passiert?
I qualified behind 6 M and during the first stint I lost around
10s to the Ms.

That behavior of the car/account is absolutely weird.
I guess some parameters which were send into the sim should be wrong.
Account
https://igpmanager.com/app/d=profile&manager=2271564

Passierte das Problem, während du WLAN, Mobile Daten oder beides genutzt hast?
Both

Ist dieser Fehler in der App, auf dem PC oder auf beiden Plattformen aufgetreten?
Both

Welches Gerät?
iPad Air

Welches Betriebssystem?
iOS

Auf welcher Version ist dein Betriebssystem?
Aktuell

Welches Betriebssystem ist auf deinem PC?
iOS

In welchem Browser ist der Fehler aufgetreten?
Safari

Kann der Fehler wiederholt werden?
First time

Zusätzlicher Kommentar:

It is solved!
No practice lap = no data for the sim = bad performance……

Tbh that’s fine and reasonable ?

It is not necessary to do practice laps. Just make sure you have the car setup saved

The way i understand it is for the drivers to establish their pace which equates to the temperature and conditions at the time of practice to the temperature and conditions of the race. The closer they match the quicker the constant pace will be and mistakes will be less. 
And also it is for fuel with no refueling,  how much you are putting in equates to the practice lap x the full amount of laps and also the push level you will run on what tires given the temperature. If you don't do a practice lap then you are simply guessing how much fuel you are putting in or you are running default fuel which is ridiculously overstated. 

This isn’t entirely accurate.  If you have sufficient records of past races, including FE for each race you can predict all of this without the need for practice laps.  Not everyone will do this and those that do have often built spreadsheets that will calculate everything for you based on the database of races it contains.  Of course the sensible option is to do both.

It's like Dick Dastardly is saying. 
I do this from time to time, and I can say that the practice info helps to set the strategy, but the consumption or speed of the car won't change if you do practice laps.