Hi J Han.
Have a 07 TM, had the same problem. There are two problems.
First, the fill hose to your tank is fairly flat. I know it looks like it dips down, but the hose is more flat than it looks.
Second, the tank has a baffle in it. I think there is a Fed law that requires that.
So, my hearty, healthy, truck-driving brother in law had a pit over which he drives his semi's to do maintenance. I drove the TM over this and looked up onto the fuel tank.
There, I found ^^%$#@)(*&)*)&&&*(((()**)) feet of vent hose coiled up on itself, and zip-tied to a stud on the top of the fuel tank. A simple pocket knife followed by better hose placement and clamping the end of the hose to the nipple on the tank, resulted in much better fuel flow. Much, much better fuel flow.
There are ramps, or other ways to raise the front of the TM up. But, sadly, I would have to recommend that you find some way to view the top of your tank to see if you likewise have 20 feet to much of vent hose taped to the top of your tank.
07 TM 40D;ISL 450 Cummins(upgraded). Very happy w/coach
Gnarly toad to scoot around.
Geocaching, hiking, fishing, National Parks, Civil War sites.