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Message: [QUOTE="Charles, post: 58065, member: 103"] Whatever's easiest. Two 44's would probably work well. With only minor changes to the wastegate duty cycle my 55 will sing right to the pin on my 30lb first stage boost gauge in an instant, with no sign of slowing down. A gate will be mandatory unless you run an obnoxiously large housing, and even then I doubt it will control it. I had a 1.39 housing on the 47 and it wasn't even close to being controllable. It would snap the pin on that gauge at even less change to the gate duty cycle. Even if you managed to control the first stage without a gate, it would be a vicious monster coming onto boost IMO. With no gate to soften the hit by opening as it lit, it might light off like a semi just rear-ended your truck. For example, sometimes people will set the gate so that it will run ____psi on spring, which is higher than their intended boost, and then they will have a controller that sends ____psi to the bottom of the gate to oppose the spring and allow the gate to open as boost is reached. In this system, when/if the signal line ruptures the boost will jump up to that governed by the spring. Which for a second stage, can be a monsterous jump, and when compounded, can wrap a boost needle around the pin in a hurry. On the contrary, if instead a person used a spring that was a bit lighter than what would hold the boost they desired, as you suggested, and then ran boost to the top port to supplement the spring pressure so that the desired boost was achieved, if/when the signal line ruptured the boost would simply fall off and the driver would notice smoke and a sluggish truck. No biggie. The ultimate plumbing circuit from a performance standpoint is to have the spring set as above, so that on spring it will hold boost below what you desire, and then have a 4 port solenoid that will feed manifold boost directly to the top port when off boost, and then start to switch to the bottom port as boost rises. In this way the gate valve can be made to stay perfectly shut until just before the desired boost is achieved and then all the pressure can be diverted to the bottom port to snap the gate open. Once the ramp rate and steady-state values are dialed in well overshooting and valve bounce can be all but eliminated and you get a system that pins the values you want very quickly and very accurately. It's still relatively failsafe in that in the event of the bottom port line blowing off the solenoid will still cycle to 100% duty cycle as the controller attempts to quell the rising boost pressure and the additional pressure added to the spring via the top port will be vented through the solenoid exhaust port and you will be running on spring only. The boost will be higher than it should be, in that the bottom port wouldn't be receiving any signal to oppose the spring and open the gate further, but it wouldn't get as out of hand as if you were running on full spring with a bottom port only setup. The most failsafe is obviously the top port controlled setup where the spring alone will not support the desired boost. Do it. You know you want to tell people you're running triples... :D [/QUOTE]