The most effective change is from badly to awful. Because "badly" is an adverb, feeling badly is doing a lousy job of feeling. The notion suggested here is that to feel awful is to have unpleasant emotions.
Making a bad condition much worse is the proper definition of the word "aggravate." In professional writing, it shouldn't be used to signify "to annoy."
Typically, in phrases with two separate clauses, commas are placed before coordinating clauses like "and." Semicolons and periods should not be used with this sentence as punctuation. No punctuation is required before the conjunction since the clause after "and" cannot be read as a sentence on its own.
There are multiple requirements, yet only one prerequisite—poor gas mileage—is mentioned. To meet the requirement, the plural form must be transformed to the singular form.
Despite being a subordinating conjunction, "although" appears at the start of a dependent clause (a clause that cannot stand alone as a sentence.) The dependent clause becomes an independent clause when the word "extreme" appears at the beginning of the sentence. "Have" agrees with the subject "conditions" as an auxiliary verb.
The most effective change is from pour to pore. Pouring something means making it run; poring over anything means looking very attentively at it, as when seeking for accounting tricks, for example.