checking valves is easy, here is a link to the procedure.
don't mess with a stock lift pump, get an airdog, fass, or raptor. I have the airdog 150gph and does great. for 400 you can get a raptor, or for 530 you can get an airdog. pm me and I will send you a link to where I bought mine, they come with filter, water seperator, 1/2" line and all hardware. best money you can spend on these trucks. edge comp is adjustable 40, 60, 80, 100, 120hp and the juice with attitude is the same with gauges. quad addrn I believe goes to 180hp and has gauges. I have the juice but thinking about moving to the quad since it has more adjustments. I have towed 10k plus multiple times w/o problems with egt or anything else.