help with code 1221

[xphilter]

hi everyone,
so my cars been running great the past couple months (since i bought it) but tonight about a mile from my house the CEL came on and i lost most of the power. i coasted for a while and had to push it up my hill but then i did the stomp test and got code 1221. I've looked through the forums and from what i can tell is that its probably not the o2 sensor but maybe a vacuum hose leak. I am pretty new to major repairs (just bought new timing belt to replace this week heh) and i have no idea where to look for a leak. so if anyone knows please help.
90 525 (m20). thanks so much
-amir
update: i let it sit for a while and it ran pretty good, enough to get it to my grandfathers shop...but then i tried it again and its ruff again but no CEL.