I call bs. As long as they are the same OEM frequency they should be fine. I'm willing to bet that their cheap aftermarket tpms sensors are not the right frequency to pair.
I wouldn't make any mention of your ECU flash to the dealer. I would just take it in and have them relearn the tpms sensors. I would think an ecutek flash has 0 impact. PM @
Visconti or have him reply here.