Roushracing2005

I have a 2005 f150 fx4 with the 5.4 and a non-intercooled roushcharger. I want to start with that I'm working on this problem currently with my tuner, I just wanted to see if I could see if anyone else had a similar problem... During normal driving everything is fine, but when I'm going through hills and coasting downhill a lot, occasionally I'll go full lean on my wideband and my short term fuel trim will jump to 1.30...(I know that's normal) but, when I get on it again it spudders and shakes with my wideband giving around 17-19... Clearly a lean condition. Is there a separate part that engages the cutoff during deceleration? FYI this is my first post and I've done a lot of searching. If this thread exists somewhere else plz let me know...