code 0171/0174 lean

2000 e-250 triton v-8 , codes 0171/0174 lean left bank ,lean right bank.
Any ideas ?

Yup. I'd bet the MAF sensor is just dirty.

While the MAF in this truck is not out in the open, they are easy to remove and clean once the air filter is out.

DO NOT let anyone (stealership etc) sell you a new MAF, they are completely cleanable and rarely go bad (99% of the time they are just dirty).

I'll try that, thanks. Also for a while now when I slow down the engine will try to idle way down and almost die. Not long after it started this I replaced the idle air control valve w/a new motorcraft valve and the problem went away for around 3 or 4 days and then started idleing way down again when I come to a stop.Could this be a symptom of the same problem?

On the Triton V-8s, I've seen a lot of pcv vacuum lines leaking at the back of the throttlebody. It should be an elbow that just slips over a nipple, usually they flatten and tear. That always causes a 171/174 code.

I cleaned the M A S today and reset everything. I'll check the pcv line as soon as I can. Thanks.