Sometimes it takes more than thread advice to solve a problem (most of the time).
I'd suggest you take it to a mechanic who can both look for codes in the various control systems as well as look at live data while driving the car to see what's happening.
There are many variables. It could be the EZL having advance issues due to knock signals. Maybe it's plugs. It could be clogged injectors. It could be a problem with the camshaft advance or camshaft position sensor. None of these are easy to diagnose without the proper equipment and sometimes not even with it.
Throwing parts at the problem could easily exceed the cost of a proper diagnosis.
My $0.02 on this one...