yes there should be at least 3-4 inches of tubing between the MAF and the filter. but i dont think thats causing the code.
what MAF and injector tables are you using? the ones on this site for the Lq4 and the 42.5 injectors are wrong, they are way too big. i started out with some files from HPT that people had posted and have started tuning from there. what do your LTFT look like?
bill, can answer those questions. i did not go over the parameter with him but its a question that need looking into.