If it started right after dealer mb (ask me what this means) significant disassembly,check for ignition components,cracked-bent-unseated-broken-over flexed,etc.this will make the spark jump off before getting all the way to the plug gap.Highest spark requirements are at leanest cruise A/F ratios-if tipping in the accel pedal makes the hesitation go away start there,if still hesitates under load increase-check fuel pressure,filter,dirty injectors,etc...in that order.....T C