My smog pump is royally debunked... i have a smog pump from an s4 engine (88) and they look very similar... and i don't wanna fork out a g for a new one... besides a small (like mm's) offset in size, is there any reason not to use this pump?

Costs nothing to try it, but if it doesn't work, you can likely get one nearly free on the FS threads.

I believe they mount differently, I'm not positive though.