LPTinc

I have an 2004 Mack Granite CV713 with a 370hp Ami engine. When I shift to the next gear I end up at about 1200 - 1300 rpms (to low) puts me out of the power curve. Couple friends have same truck and does same thing. I read on here about changing exhaust manifold to older style (much bigger ports) and change over from my 3” turbo  to a 4000 series 4” turbo. Truck come alive with power. It’s been a while since reading the article and want to know if I’m correct in what I said was in the article? Thank you 

I just bought a 2004 Mack cv713 Granite, tandem axel dump truck, 370 hp with the mack 10 speed trans. 22.5 x 4.25 front and 24.5 rears. My issue is when loaded, when I shift I loose to many rpms and it takes me out of the power curve, it will pull out gradually but I know it's not good to lug the motor. The trans won't let me shift any faster like my eaton 8LL. I have to let rpms drop, I find myself sometimes in the 1200 rpms in the next up gear if pulling a slight grade. I can't stay in the power curve. As with my other trucks, 1450- 1500 rpms is where my power is. Suggestions?  I'm thinking transmission change? I'm not sure of the gear ratio in the rear but at 70 mph I'm at just over 1800 rpm, a friend has an 06 same setup and tells me he's 80-85 mph truck witch I don't doubt. I feel this could easily fixed with the wright combinations. Suggestions? Thanks, Lou