the only way to see what the maf value is easily is a live data scanner compared to specs. if you have cleaned it, its likely bad.
the 440 is the broad "leak code" and there are a million things that could cause it. any leak in any part of the fuel system. the most common for those is the vent valve though because from the factory put right where it can fill up with junk and get stuck open. that causes a leak code. there are a number of valve relocation kits available, i used the one from napa when i did my old mans, it comes with a valve that uses some rubber hose and you buy some extra hose and put it somewhere else. some put it above the trans, i just put it high in the fender where the salt doesnt go.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock