Drastic mileage drop after timing belt change

I had the timing belt changed after 150K (BAD), tuneup and my mileage has dropped from 17mpg to 12 mpg city driving. anything jumps off the paper?
2004 Tacoma, 6 cylinder SR5

 

All I can think of, is the shop didn't align cam gears properly, and the valves our out of sync with the crank.

 

This. Only thing I can possibly think of, unless other things were done as well.

 

how long ago did you get the truck back?

 

less than a month ago. Noticed mileage drop next fillup

 

Maybe the mechanic "borrowed" some gas while you weren't looking... ??

 

Does anything else seem odd? Idle, power, strange noise, etc.

 

no. it feels the same

 

what should the timing be for that v6 engine ?

 

Your timing is controlled by the ECM. You can not adjust it.

 

but can the timing be checked externally to see if this is the problem?

 

Ignition timing changes continuously while driving. You can hook up a Scangauge or Ultragauge to moniter it.