There are plenty of synonyms for the phrase "affect favourably" that you can use to diversify your writing and express yourself more clearly. One word that closely relates to this phrase is the term "benefit", meaning something that brings a positive outcome or advantage. Another synonymous term is "enhance," signifying a process of improving or making something more attractive. The phrase "improve upon" also fits into this category. Another related word is "favor," suggesting a positive disposition towards something. Other synonyms include "boost," "promote", "advance" and "facilitate." By using different words that express the same idea, you can make your writing more interesting and precise.