There's a device on the turbo activated by intake manifold vacuum that prevents sudden throttle changes from causing turbo surges. It has a rubber diaphram that starts leaking after a while and produces erratic turbo operation. In the case of my 740 (Mitsu Turbo) it has a really bad leak and causes a severe missing problem whenever the turbo is activated. I took one from a wrecking yard thinking they were all the same but they're not. Mine has about a 1/2 inch section that goes into the turbo housing and this one goes in about 1 3/8 inches. If you need one let me know: lgspooner@adelphia.net You can test it by putting a vacuum pump on the vacuum tube connection. If it holds vacuum it's OK. Or you can push the plunger in w/ a screwdriver and then put your finger on the vacuum hose connection. Release the plunger and you should feel suction at the connection. No suction no good.