You can find downpipes for the Explorer but the bigger issue is you being in CA. How are you going to pass emissions? Downpipes will fail. Not CARB approved. You would have to go back to stock tune as well to pass. If you want to go big get new fuel tank pump, new HPFP, meth, exhaust, intake, larger turbos, plugs, upgraded intercooler, E85, 3 bar MAP, and push boost/timing until you knock, pop a piston, smoke the clutches in the trans, or roast the PTU. LOL. Not sure where our injectors max out at. I am running a very mild setup. Also weight reduction could be huge. I scale out at 5,030 lbs with me and full fuel. That is a lot of weight!