Pics of MAC Plenum

Gotta love MAC quality (or lack thereof...)

they look just like my C&L. inside look about same too. They prolly same darn thing, just diffrent name..

inferno9898 said:

i just ran some errands to get a better feel for the problem, so im going to let it cool down before i go and mess with it some more. i was thinking IAC too, because the idle is hanging up around 2000 at times with the throttle closed, which in my mind means air is getting in somehow. thats something the IAC would allow, so i'll go make sure i put it back on right in a little while. its really weird to drive it right now. because the rpms are trying to rise to about 2k, ill let off the accelerator at 1500 in 2nd gear or something, and the car will slowly accelerate. i'm almost fighting the engine when i go to brake.

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Oh....this again. This happened once to me with a Mac 70mm throttle body. What happened was once I ported and polished my upper intake, the 70mm throttle body caused a high idle do to the fact the throttle blade wouldn't close all the way no matter how much I adjusted that little screw. I even had a peformance guru around here look at it and he agreed, it was the damn throttle body. I ended up having a high idle, not quite as bad as yours, and it ended up throwing a P0156 code for IAC overspeed. The only thing that fixed the problem is when I removed the throttle body and went to a 70mm throttle body from FRPP. Much better quality and better performance with the FRPP piece over the mac crapper. Problem was solved. I called Mac performance and explained things to them. They didn't want to do crap about it. Imagine that.

In your case, it sounds like either the throttle blade isn't closing all the way or there is an air leak somewhere. Double check for air leaks and make sure the throttle blade is closing as it should be. Report back and if you get the check engine light, get the codes pulled and post them on here. Then, we can help analyze the problem even further.

StangPro said:

Gotta love MAC quality (or lack thereof...)

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Yeah, tell me about it. :damnit:

I got the MAC polished plenum, just cause I thought it would look nice under the hood. Whats the difference in plenums anyway, 2-3 hp, and thats at what 5000 rpm, so i figured get the cheapest one I could. Anyway, there was a problem with mine when I got. The metal piece that holds on the vacuum line on the back of hte plenum was bent upwards and I had to bend it back, otherwise it would have had interference with the throttle cable. Anyway, one pic below...

in my opinion...

i have the mac plenum w/ the accufab 75 mm TB. the mac aint pretty. i don't care how it looks because im not trying to win a car show. i bought it for performance and as far as i could tell there is absolutely NO difference between it and the C&L. it works great and is cheaper than any other plenum besides the granatelli. i run high 12's all day long with a 2000 gt w/ nothing but bolt-ons. i could always go back and powdercoat the plenum if i felt like it.