1.5 jdm engine dud?

hey i recently changed my air and fuel filter and no change in my performance i need help is my 1.5 jdm engine a dud or do i need to go around fixing different parts off this junkyard rescue i hear that my noise which is kinda like a loud puffing sound and kinda like my engine sputtering and the longer it runs the more of my power goes away.
can someone tell me what the problem would be if as my engine heats up i loose more power? it's supposed to be a brand new engine but it did this before the engine swap too i think i couldn't really tell cause it smoked too much, please help.

i'm guessing no one has any idea what is wrong but the mufler shop said sounded like i needed a tune up.

it smoked before you bought it?

it needed a new engine and it was only 550 w/ perfect body.