I adjusted the timing on my car a couple of weeks ago to factory specs. Afterwards, it was driving like a peice of ****. It was running rough as guts and really sluggish. So, I rechecked the timing and it reported OK. (13° B.T.D.C. with jumper disconnected, 5° with it grounded)
Even at idle, it just didn't sound healthy though. So last night, I continued to advanced the timing until I thought it sounded healthy. (it was about another 5°) Anyway, the result has me a little puzzled. It's running beautiful now. Responsive, got some power back and idle is nice and smooth.
I'm a bit concerned that I may have uncovered a bigger issue here. I'm not quite sure where to start to work out why this is. Has anyone got an ideas?

The outer ring of your harmonic balancer (bottom pulley) may have just slipped.

Take out #1 plug (or all of em to make it easier) hold a long thin screwdriver down the hole so it touches the piston.

WARNING. Under NO circumstances during this check should you have your ignition on or use the starter moter to turn the engine, this would be very nasty. Make sure the screwdriver does not get jammed as the piston comes up.

Get a second person to turn the engine slowly with a spanner on the bottom pulley until the piston comes up to the top. You'll feel it stop moving.

At this point the timing mark should show top dead centre (tdc).

If it does you may have some other timing/computer issue.

If it doesnt the ring may have slipped, this isnt critical but I would advise replacing the pulley, as once they have slipped they tend to separate.

If it separates you will loose drive (Fan belt comes off) to your alternator and P/S. The water pump is on the other end. You will be able to drive home on the battery if this happens but the steering will be heavy. :D