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Message: [QUOTE="Charles, post: 91640, member: 103"] I always run a super soft spring with a dual port gate so that I can use manifold pressure to easily alter the spring rate by adjusting how much additional manifold pressure I let impact the diaphragm through the top port. This way you're not out there swapping springs a zillion times for no reason. The spring should be strong enough to hold the gate shut until manifold pressure begins to climb. That is all. As soon as you have manifold pressure you have force to hold the gate closed, so why dick around with a mechanical spring when you have an infinitely variable air spring at your disposal??? Aside from this, there is one other point I would like to make. And that is the concept of failSAFE operation and design. If you set your system so that manifold signal must be present to OPEN the gate, and you blow that line... you will overboost, which could be devastating depending on the system capabilities. This for instance would be the case if a person ran a lot of spring and then had a signal line to the bottom port oppose the spring as manifold pressure rose, and lift the valve open. Well.... if/when you rupture that signal line you now have no wastegate signal. The engine will then run boost right up to the mechanical spring force. You're "on spring" at that point. Could be a nightmare, especially on a compounded truck. I know.... I've done it, a FEW times. Snapping a 100psi gauge when you're set for 70psi isn't my idea of a good time. Contrary to that methodology... if you instead were to say, set the spring so that it would NOT achieve desired boost, and then regulated the pressure to the top port then you could control boost without issue. The difference being.... if/when you rupture the signal line you LOSE boost and drop off like crazy. Truck drops power and starts smoking. That's FailSAFE operation. Something that tends to keep the coolant IN the degas bottle and the rods IN the block on a truck that gets driven enough to see hose failures from time to time, which is any daily driver. Last point..... seriously consider using very high quality signal lines, preferably braided stainless rubber lines with AN type fittings. Signal lines blow OFTEN in my experience. There is a lot of sh*t going on under the hood, and with the heat and time, plus relatively high pressure [i]at[/i] relatively high heat, it's a rough environment for a hose. Most hose that comes with controllers and gates is IMO insufficient. [/QUOTE]