As you are expecting more than an average score I would say you must cover all chapters. You can follow some other strategies too like At least visiting previous year questions of the topics that you have less prepared. You may also refer to  40days crash course book by Arihant for covering all the topics.

Hii aspirant..

If you really want to do very well and score very good marks and I would recommend you not to left any stone unturned. JEE mains exam have a vast syllabus and if you are really willing to do score good marks then you should not left any ask for syllabus for the examination. 

Go for as much as mock test you can which will help you to increase your speed also and try to solve previous year question papers because sometimes same questions repeated with a bit of changes. Try to complete all the syllabus on time so that you would get trying to do a final revision before the exam.

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At last best of luck. Study hard and do well.