ok so i've replaced the fuel pressure regulator, replaced the flex hose between the maf and throttle. should be ok, go for a test ride, check engine light comes on in about 5 min. go home stop car and when i shut it off, i hear a hiss of vacuum release right away. i suppose somewhere in this process i've created a leak question is, can i just pull the vacuum hose that goes through the firewall and put a golf tee in it to seal it off to at least see if the vacuum is the issue.

also i suppose now that i've fixed the fpr and the flex hose, there is a chance that my o2 sensor is actually bad. the only symptom i really have is that the power curve is not very smooth, there are flat spots. at constant speed, it feels like it sputters a bit, but it's so very subtle it's often hard to tell if it's bumps in the road or gusts of wind.