I have a 2012 GCL thats been having an issue. When I step on the gas it seems to hesitate and buck until i reach a certain speed. It almost feels like a clogged fuel filter but my mechanic tells me they no longer have them. We did a complete tune up which did not resolve the problem. No diagnostic codes come up when he puts it on the computer. He feels it may be a torque converter issue but is unsure. Any help would be greatly appreciated.

thanks
Tammy