In the first example, "knew" in the protasis and "would" in the apodosis are in the past subjunctive whereas "was" in the protasis and "was" in the apodosis, both of which are emboldened in print just as I have emboldened their equivalents in the second example, are in the simple past tense. This is how many native speakers say it now because they try to align the verbs in subordinate clauses so that they look like their past subjunctive counterparts in the main clauses, and each example above does mean the same thing as it would if the verbs in the subordinate clauses were in the present tense, i.e., in the second example, "is" and "will" instead of "was" and the second "would".
In essence, what I am trying to say is that it could be said this way as Andrew has stated in his comment to your question above:
"If I knew that he is cheating (now), I would tell you
what is going on."
"If I were the person who is in charge (now), I would do it
this way so that no one will be the wiser.
This second way is less common and it clearly shows the subjunctive verbs. It is a matter of style in English now. Do you want to clearly point out that the information in the subordinate clauses are happening in the present tense or do you want it to appear to align in form with the past subjunctive verbs of the main clauses? That is often up to the writer or speaker who is using these constructions. The subjunctive is a tough subject in English because it looks so much like the past and present tenses in Modern English. Because of this, the rules are all over the place. I would tell you that you could use both "you are trying" and "you were trying" in your original example and you would have the same meaning because this is a rule that is not consistent in Modern English. I wish it were an easier subject to explain.
