Cost of injector cleaning...
It cost me nearly $300. That is because I could not find the cause of my rough idle. I checked compression, ignition, vacuum leaks, the famous OVP, and could not determine the source. I even checked the distributor (under the rotor) for worn out weights, etc. I finally gave up and gave it to a local mechanic who spent quite a few hours analysis (though did not charge me for it). He checked the distributor and the oscilloscope reading was normal. He finally found the source to be the fuel system. I had long given the fuel the OK since it seemed to run fine under high RPM. Anyway, he pulled out the fuel distribution, cleaned, added new gaskets, and now the engine runs smooth.
BTW, I agree with the throttle position sensor. That is a quick replacement and cheap. In my car, even the return springs for the throttle was gone/worn out. This car was ready to be donated by my friend and I rescued it. All it needs is a little TLC and should run fine. I just drove it the 75 miles to work to see what else it needs (need to keep the miles in my bimmer from creeping up too). It has a sound coming from the differential. Or it could be the bearings. I shall see, with 250+ K miles, what else may need replacement. Yes, the struts will be replaced when I have time (probably in 2 weeks from now).
Hope this helps, Hector