hustler not running good

have a hustler super z 30 hp kolher. runs for 10 minutes blades engaged or not. will start right up then lose power after 10 minutes have to pull choke up to keep running. Brought to shop and they replaced all fuel lines and filters, fuel pump and cleaned carb. Said rebuild was not needed. Brought home and ran good for 20 minutes. Brought back and they cleaned carb again. They said they let it run for an hour and didn't have problem. When I first brought it in it acted up and they good only keep it running with choke pulled. Mower is 2007 with 151 hours. Only used for home with 2 acres. First 6-7 years never a problem.



Any help will be appreciated

Dave S.