I think that when they went to Tier 3 emmissions, Ford was having a little issue with over-fueling the Diesel PArticulate Filter (DPF). The result was the excess noise and flames. Just what I heard so don't "roast" me on it.
OH&S actually sent out a notice to us to not allow ANY of these trucks onto our leases until it could be proven that the recalls were done... Pretty serious risk of something going boom.