Less of an angle is best, but 45* is fine, most people use that.
I think most pre-04 use 45* because a 22.5* pipe would bump into stuff on that side of the engine bay that the 04+ people dont have, so we have more room to use a smaller angle...
Im starting to suspect that maybe my pipe was just too long or something.
I'll take some pictures tomorrow, the biggest problem I had was that my MAF was bolted into the stock airbox, not clamped on with a screw-type clamp like on all the other pictures I've seen. The result of that was that the filter had a very very very small lip to clamp onto and kept slipping off the moment the clamp began to tighten.
It's kind of ghetto rigged, but it works great so far. I just put 2 zip ties through the bolt holes on the MAF and strung them under the clamp on the filter, and back around. Tightened the filter down a bit and then snugged up the zip ties as tight as I could. Then I tightened down the clamp as tight as I could.
The zip ties hold the MAF onto the filter and the clamp seals it up.
I've come to find I have some weird pain in the ass California emissions package that it seems like nobody on this forum has, lol. So I had a few extra things to deal with when I did it, like an air tube that went into the stock air box to feed a smog pump/air pump, I just got a crankcase breather filter and crammed it into the hose and clamped it down.
I dunno if you have the same MAF I do, but if yours clamps onto the air box like a normal one there's really nothing to worry about.
This will work great if you have a normal MAF that just clamps on, this is vailskier's setup