Oldsmobile/Buick Repair: silhouette misfire on #6, compression test, valve spring

Question
I have a 98 Silhouette that has a misfire at idle, under acceleration,and while
cruising.  It will maintain speed once you get there, but it misses as soon as
you try to accelerate.  The check engine light is on and flashing.  The code
tells me it is a misfire on cylinder #6.  That cylinder had low compression, so I
removed the heads & had the valves redone.  Whie I was at it I replaced the
plugs and wires. It started and ran fine when it was back together.  About 4
months later it started missign again.  Same code - misfire on cylinder #6.  I
decided to try a new ignition coil.  While driving the van over to the garage I
work at it stopped missing and ran fine.  It was great for about 2 more
months, then started missing again.  I still had the coil I purchased earlier so I
decided to give that a try.  The new coil is on but it made no difference.  It stil
has the miss.  Where do I go next?  Should I try an ignition module or
something else?  I would appreciate any advice you could give me.

Thanks,
Scott

Answer
Actually sounds like a problem I had with a broken valve spring. I would do another compression test, and observe the actions of the needle on that cylinder, compared to the others, even if it reaches the same pressure.
If the needle acts strange, it could be a valve not seating every time.

Van