SilverSS/SC

My long term fuel trims used to be pretty steady , they would vary obviously , but the correction factor wasnt much . Lately though the car is acting wierd . Theres times where the fuel trims are normal like b4 , and now there long periods of time where acts as if adding alot of fuel to compensate for lean condition . Typically +19.5 at idle and +12 to +17 while cruising , but at any given time can just go back to the +2 to +3 its normally at . I was sitting at a light yesturday just idling in nuetral , LT trims were at 0 , then shot up to +19.5 and the idle got a lil rougher than normal . Different weather conditions dont seem to effect anything . The car also now obviously sets a 0171 lean code and also sets a 0300 random misfire frequently with really no symptoms of a miss ( bkr6e plugs are new , coil paks good )

1 thing that may be causing a prob , but Im not sure of is lack of the PCV hose being connected to the intake . When I switched to a LT1 mass air meter and IAT I made a custom intake and didnt add a nipple to reattach the hose . So I used a breather on the valvecover . Could that be causing my random problem ??? If u answer yes , please explain . On my LT1's I vented the crankcase with a electric air pump , not sure how unhooking the pcv effects the bitchy cobalt pcm . I know I could just provision the custom intake to test hooking the PCV back up , but Im so swamped with my job and working on other peoples cars I dont have time to mess with my own ...so questions I ask .