I'll get right to the point. My car has been running like complete sh*t lately, and has been acting like it has a huge vacuum leak- idling at 1500-2000 + rpm, rolling idle, very jerky off idle, short term fuel trims changing. The problem started off almost unnoticable this spring, and has become progressively worse. The manifold will not respond to any conventional method of detecting vacuum leaks, though- I have sprayed carb cleaner and soapy water all over every gasket area, and it won't draw any in anywhere.
To make a very long story short, I have probably had the stupid blower manifold off and on the engine probably a dozen times in the last week. I have tried replacing gaskets, resealing everything, planing every gasket surface, plugging off every vacuum port, attaching the MAF directly to the throttle body, swapping complete throttle bodies, swapping IACs, swapping TPSs, leaning and richening the closed loop tune, and a bunch of other things, without seeing any change in the way that the car runs.
I talked to T.C. about it, right before he went out of town, and he suggested swapping the stock upper intake back on the car to see how it ran. At the time, I didn't think it was necessary, but I finally did try running it for a minute with the stock parts back on it; the engine ran beautifully that way.
I had tried calling Alpine for probably a week straight, and the number on their website was disconnected. I PMed dmdicks, since he's a personal friend of John at Alpine, and he failed to respond.
Finally, after getting so sick and tired of beating my head against the wall that I was driving myself nuts, I had an idea. I decided to soak the manifold, while still on the car, with soapy water, and pressurize the manifold with compressed air.
What I saw shocked me; there were air leaks all over the manifold! Fortunately, I had my trusty camera with me, so I repeated the test on film.....it was very dramatic.
There's a frame from the video I took of the test. The little red arrows depict the air leaks. There were actually four that I saw; from the throttle cable holddown bracket bolt hole, around the heads of the two longest upper to lower IM bolts, and one that was leaking right through the aluminum between two of the runners.
Now I realize that these probably aren't the sole cause of my vacuum leak problem, but it clearly demonstrates how porous the Alpine manifold actually is. I'm willing to bet money that there are a bunch of little holes all over the manifold, in places that I'm not able to reach. I don't have any way of pressurizing the manifold once it's off the car, so I can't check the underside yet, but I'm going to make a set of block-off plates which will allow me to do so.
To make a very long story short, I have probably had the stupid blower manifold off and on the engine probably a dozen times in the last week. I have tried replacing gaskets, resealing everything, planing every gasket surface, plugging off every vacuum port, attaching the MAF directly to the throttle body, swapping complete throttle bodies, swapping IACs, swapping TPSs, leaning and richening the closed loop tune, and a bunch of other things, without seeing any change in the way that the car runs.
I talked to T.C. about it, right before he went out of town, and he suggested swapping the stock upper intake back on the car to see how it ran. At the time, I didn't think it was necessary, but I finally did try running it for a minute with the stock parts back on it; the engine ran beautifully that way.
I had tried calling Alpine for probably a week straight, and the number on their website was disconnected. I PMed dmdicks, since he's a personal friend of John at Alpine, and he failed to respond.
Finally, after getting so sick and tired of beating my head against the wall that I was driving myself nuts, I had an idea. I decided to soak the manifold, while still on the car, with soapy water, and pressurize the manifold with compressed air.
What I saw shocked me; there were air leaks all over the manifold! Fortunately, I had my trusty camera with me, so I repeated the test on film.....it was very dramatic.

There's a frame from the video I took of the test. The little red arrows depict the air leaks. There were actually four that I saw; from the throttle cable holddown bracket bolt hole, around the heads of the two longest upper to lower IM bolts, and one that was leaking right through the aluminum between two of the runners.
Now I realize that these probably aren't the sole cause of my vacuum leak problem, but it clearly demonstrates how porous the Alpine manifold actually is. I'm willing to bet money that there are a bunch of little holes all over the manifold, in places that I'm not able to reach. I don't have any way of pressurizing the manifold once it's off the car, so I can't check the underside yet, but I'm going to make a set of block-off plates which will allow me to do so.