Are you asking whether TOEFL will help you improve on the verbal GMAT? It can help you get more familiarity with english in general which is good. Probably sentence correction is an area that can directly help you the most. But since sentence correction is learning to apply a certain set of rules, if you get the right prep that alone could help you improve. The TOEFL is just additional practice/familiarity and perhaps you'll learn a few things as you study for TOEFL.
You'll need to identify whether the weaknesses in verbal are a particular section or overall. If overall, then studying for the TOEFL will not help verbal overall significantly. My guess is that it will help in familiarity which can help in SC, and *maybe* some of CR and RC.
thanks very much for your reply.
Do you think good TOEFL score can help to offset low verbal ?