My Mazda is a 1995 626 Lx 2.0 engine. The engine idles rough when in park and at a stop sign. Give it gas and it accelerates chuging and coughing (lags and hesatates) Then during acceleration it stops chuging and coughing and runs smoothly for awhile and then runs rough again. I ran the codes and the key on engine off codes all indicate the that engine is running just fine (all read 111)! All codes including the stored codes that would indicate an intermittant problem read 111. I ran the key on engine running codes and I get the codes for hego (oxygen sensor) reading lean signal (172). And also I get cannot control RPM low RPM check (411). So far I have: Replaced the spark plugs and the plug wiring. Replaced distributor cap and rotor. Replaced fuel filter. Replaced fuel pressure regulator. Cleaned MAF device. Cleaned throttle body and replaced the throttle body gasket. checked the throttle position sensor and it's OK. Cleaned the EGR valve and checked to see that the EGR sensor is working properly. Replaced the Idle air control valve (IAC). Checked for vacuum leaks and there is none present. I made sure all hoses are connected. I also tried to tweek the little air screw on the throttle body and the butter fly valve stop on the throttle body next to the throttle position sensor. Could tweeking the throttle body air screw and butterfly stop cause the problem? Is the TPS (throttle body sensor) now out of position because of what I did? If tweeking is the problem, how do I get the right setting back for the throttle body? Or what can I check to see what is wrong and get the car running right? Replacing stuff hit or miss can be really expensive. Can any one help with advice?