What could cause a PO170 on a 2000 Mitsubishi Galant after replacing a blown motor

Question

Hi I blew an engine on a 2000 Mitsubishi Gallant and put a 2003 engine in it after I put the engine in I got a PO 170 code. I took it to a shop and supposedly it does not have a air leak or exhaust leak in the short-term fuel trim is reading in between three and five and the long term fuel trim is reading 12.5 constantly. What could be causing this problem?

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Answer 1

Long trim is that high fuel pressure has to be checked,  vacuum from a open purge valve or EGR , vacuum line not in the right places