Will I be sinful for this work of mine, knowing that the source of the company owner's money depends on raising prices on the other company where my manager works, and should I leave work immediately or wait until I find another job?

An agent in buying or selling is not permitted to buy from or sell to himself without the principal's permission, due to the suspicion involved in such a transaction. The questioner should advise the owner of the company he works for and explain the Shariah ruling to him. If he does not respond, then he should explain the matter to the other company. Otherwise, it is better for him to leave his job with this employer.