Fuel trim can be caused by vac leaks or fuel pressure regulator.
Pull vac hose off reg and see if it drips/smells gas. If it does , change it.
Also look at all vac hoses ..usual suspects on 104 HFM systems are the white plastic hose going across front of engine , under engine front cover .. they heat fatique and crack..also check the cross hose from MAF for any unmetered air being allowed to enter engine.