I've got a 2006 Dodge Grand Caravan with a 3.3L engine and 236,000 miles on it, I wanted to test out my fancy new BlueDriver and discovered that in addition to the ambient air temperature sensor being disconnected (I knew about that one) I found a P0171 code for System Lean on Bank 1. When I checked it, the system was lean by 30-40% so I wanted to fix the issue. I needed to change the valve cover gaskets anyway so I went to work and found some rotted crankcase and PCV hoses that I replaced but that hasn't even made a dent in the issue. What can I do to troubleshoot and find vacuum leaks effectively without buying a smoke machine? The car doesn't run any better or worse since changing out the hoses but it's guzzling gas, I only get 19 MPG highway. Or should I just go straight for the O2 sensors? Thanks!