slight irradic idle

My car is a 1995 Buick Regal Gran Sport Coupe (my favorite style - the 1995-1996 Regal coupes :) ). It has the Vin L 3800 SFI/TPI engine (Series I 3800 with composite intake plenum) with 157K miles on it. I've has the car for almost 2 years and it has always idled slightly irradic but it is barely noticable. It seemed to run perfectly fine other than this. A couple days ago it wouldn't start right away the first time like it always did. However when I tried to start it again just after the first time it started up and ran just fine and the Service Engine Soon light stayed lit. The car did this one other time about a year ago and I haven't had any other problems other than the slightly rough idle. I borrowed a scan tool from a local shop and found a very odd code 361 - EST not toggling. I don't know how to interpret this code. I did notice a random misfire when I watched the realtime data. I have already replaced the Throttle Position Sensor, EGR Valve, Idle Air Control Valve, PCV valve, Purge valve, spark plugs & wires, air filter. The all three coils and the ignition module test fine tested good. I have no vacuum leaks. I am suspecting a faulty Crankshaft Position Sensor or a Camshaft Position Sensor even though no troublecodes referring to either part are present. I would just replace both but money is tight :( . Any advice or guidence would be greatly appreciated.