First let me say. Why when some ask a simple question must you such a rude dude.
As I have seen before you don't read the "whole post." Tirebite said use a gauge.
Look at Tirebite signiture. When it say's ASE Master. That mean he has taken and passed a battery of test. And is a working professinal mechanic.
What you are doing has become common in auto repair. That's just keep changing part and some time or other you will stumble on to the problem and fix it.
Your point of cost effect. Does come into play. But if you want to fix the car you must pin point the problem.
The problem that was stated at the top of this post appears to be low compression. And a leak down test would be in order to isolate the problem.
I have seen treads in the archives to show how to do both properly. And interpet the data the qauges give you.
Charlie