As I said earlier I would first look for a vacuum leak. After confirming there are no vacuum leaks from what you have said about plugs and wire being replaced already I would do the following. As you may have a compression issue a plug inspection can tell alot.
1. Get a engine compression tester (purchase or rent)
2. With a cold or engine that is cold enough to work on comfortably Pull each plug and look at them the should look very similar they should not look oily, fuel wet, coolant wet or other conditions better to google for examples.
3. Now to do a compression test
a. remove fuel pump relay have a friend crank the engine until you signal
them to stop usually 7 rotations you stop when the needle stops moving
up. You will see the pattern. Do each cylinder the same rotations record
each reading. with the Throttle plates open I do this by placing a Screw
driver handle in the throttle plates carefully. Or use a remote starter
switch then don't pull the fuel relay.
4. If a reading is about 10% from highest to the lowest your fine outside of
the u need more diagnosis.
5. If the readings are outside of 10% and below about 120 psi you can do a
wet compression test by squirting 1 or 2 squirts from a little oil can of
motor oil or atf and redo the compression test.
4. A lot of people do another test called a leak down test I find this is usual just extra work as this tells you enough. Good Luck