Rough Idle right at 10MPH

This is regarding my '02 SR5 3.4 with 134K. This is a needle in the haystack type of scenario. When I slow down as soon as I hit 10MPH she starts to idle very rough, at times it feels like she's about to die, and than when I get to a complete stop the idle smooths out and runs just fine. Same when I accelerate up to 10MPH if I am accelerating slowly. So basically a rough idle 0-10MPH and perfectly smooth after that. So far I have cleaned the TB, MAF Sensor and replace the Air Filter. There are no CEL, no Vacuum Leaks, nothing. It appears a Tune Up was recently done, too (I bought her with 133K). It is unknown if the Timing Belt was done as "normal maintenance" at 100K. The previous owner is out of state and won't be able to get back to me until he gets back and looks over his paperwork to see if he ever had the Timing Belt done. Obviously I don't want to replace things that don't need replacing and as the shop/mechanic told me, without any other "symptoms" they could end up diagnosing for hours and still not find anything, which would also be costly. So, with that said, any ideas?