In SA the highest rated Octane fuel available is 95 Octane (RON I think) and even this is of questionable quality and can vary drastically between stations at times. I also had the noisy crickets. Recently I tried some Liqui Moly Octane Plus for a run we did to see if I can experience what the car would feel like with the proper fuel. Noisy crickets are gone and for this last tank I only used a 1/4 bottle and have run the previous tank down to about 6 litres. Car was a lot smoother through the revs and quieter at idle.
Not sure if it's a fix but it helped me a bit.
I'm on about 26000km (approx 16230 miles) and this is my everyday runner with no real mods at all.
http://www.liqui-moly.de/liquimoly/mediendb.nsf/gfx2/2527.jpg/$file/2527.jpg