Low Idle and poor MPG HX

[themow]

So I posted last week but have since done multiple things to my car and my problems have lessened so I figured Id start a new thread.

97 HX 5spd Federal version. 220k
New ECU and exhaust manifold. Recent tuneup.
Started acting up badly replaced ECU problems went away. Replaces ex man since mine was cracked. Prior to replacing manifold, was getting p1162.

Now with the new manifold and I cleaned the carbon off my wideband, Im not getting any codes but I am getting poor mpg. Probably around 30 not positive yet. Can the wideband be bad and not throwing a CEL?