It's not a problem with sniffer testing. However, certain places require a visual inspection, so it's their job to look closer. If they don't see a pulse-air system (for pre '85 Eagles I think), it's a dead giveaway.
I agree, the emissions from a TBI is probably better than even the best working carbed 258 with working emissions equipment. Even if it is though, none of that matters under law unless it has the sticker to prove it. Shops in my county will not easily overlook these things, and a 30 year old car only makes them look closer.
That being said, if you can make a setup that looks even remotely close to the original system with egr, pulse air, etc in place, you can potentially get away with it. Heck, the air pump doesn't even need a belt, it just has to be in the right place and look like an air pump.
This gets me a little more worried since the Eagle is my daily driver and needs to pass when I send it in, but I wouldn't want to risk spending ~$1000 on a conversion and not being able to drive it for lack of a sticker.