Inside the owners manual it suggests you use Techron (specifically) during oil changes or every other oil change (7k miles). You can lessen the effects by not gassing it too hard when it's wet/dew-y. I clean mine every time I go to get a car wash, I suggest you do the same. Also, get up in there too, the pipes are recessed and that entire port down there gets nasty. Cleaning the entirety of the port, even the top, may help you keep it a little cleaner a little longer. Also, try using a premium brand fuel (Shell or BP seem to be the best) and avoid discount stations (walmart/Murphy, local grocery store, etc...) as the premium brands usually have a cleaner fuel/few more additives. Also, make sure you're getting the right fuel, our cars use 87 octane, putting in a higher grade won't do you any favors and you won't burn it all, leaving more buildup on your exhaust ports. With saying all of that I will usually put in about 1 tank a year or Shell's Super 93 just because it has extra detergents. I don't know if it helps the engine or not but maybe. Hope any of that helps.