Thanks for the info. Going to take off the head and hope the pistons are ok. That will determine if I go any further. If so I will get a reman head. Did learn a lesson though.Generally, yes. That's assuming the belt was put on proper (gotta throw it out there, I don't know your level of experience). You could compression test to see which ones are bad before repairing, or get new head(s) and possibly pistons.
Timing is the first thing we generally suggest people do around here, as it's massively neglected, and by far the #1 killer of these engines, both GS and GT. I can't remember the last engine failure even at high mileage that wasn't a timing failure.
Your 2007 would have been due in 2012-2013 by the old OEM style belt values, then generally the next belt if they had used a cheap or performance one would have been 6 years later, or 9 years on a long life belt. Very few people actually get it done, as it's about $600-$1500 at a shop depending on where you live and who does it.
Yes, change it. It's a belt, and it's interference.My gt has 126k miles. Would you recommend I change the timing belt or chain? Idk which it is. I do not have service records and don't know if it's been replaced yet. Is there a way to test a timing chain/belt? And you said the V6 engine is an interference engine?