Okay, I have a Hino tow truck 258. When I hit the 2000 RPM my power cuts off and there's turbo lag. I bought a 4000 dollar DPF filter, rebuilt the motor head and the turbo. When I installed the DPF filter (did it myself last week) I still had a check engine light from the last filter so I went to Rush Truck center so they could take it off. I got it back today and it's still lagging at 2000 RPM with a loss of power going uphill but not down hill. before these problems, I remember towing a car in loose sand and unfortunately I got stuck so it took me a while to get out with the help of my bed which I knew that I would cause damage to my transmission. After getting stuck, these problems started to occur with my truck not passing 2000 RPM with turbo lag. My friend told me I could be the RGP valve but I'm not too sure, can anyone help me?