Injector cleaning is #1 imo. If one injector gets sticky, leaky or clogged it throws off the whole ECM fueling calculation. Not nessesarily a lot but just a bit. I run a bottle of PEA every oil change now so far so good on Chevy 6.2l truck. When scanning the engine funky injectors will show up as right/left bank fuel trims out of balance and possibly fuel dilution if you get leaky one/s