Alt=Life. If you lose altitude advantage vs FW190, the only way you can shot him down -- head to head attack...
You cant escape from FW190 and cant prevent FW190 from dive away from you if you would gain advantage.
Almost the only way you can shot down FW190 on Yak-1b -- if FW190 didnt noticed you and you have 1500-2000 m alt advantage, then you will have 1 or 2 possible attacks, before FW190 dive away with minor scratches in most cases.
Using best of the best Yak available -- Yak-9T greatly increases chances of success