So I have an 03 Ex coupe, and the check engine light has been on. I know the EGR passage is blocked at some point, and that it isn't by the valve, and the valve isn't bad. My next step was to try to get at the intake manifold, which has proven to be far more difficult then I thought. I have gotten everything down to the manifold itself off, and the last center top nut won't come off. I've tried everything from penetrating oil to wd40 to by home remedies, with no success. I have no clue how to get this off because of it's really tight position making it hard to get any kind of tools in there. Here is an image from below, looking just past the oil filter mount and the sensor directly above it. https://image.prntscr.com/image/_d7gignwSXmHHLVZyKjtGw.png
A racheting box end might work if it could be worked onto the end of the nut, but I doubt it. With a regular combination wrench on it, from above it will not turn because the intake housing blocks it. From below there is plenty of room to get it on there, but there is no way of getting enough leverage to break the rust. Extending the wrench isn't an option either, as the way the wrench sits, you can't add more than an inch of pipe before more engine gets in the way. I have run out of options, and need help. Anything would be greatly appreciated!

 

The intake manifold is a total pain to remove unfortunately.
I would probably try putting a box end wrench on it and hitting the wrench with a hammer to try to knock it lose.

Last time I removed the intake manifold, I took the cylinder head and it off as one piece - then it was much easier to separate from the head.