My 97 5 speed car with the 2.2 recently jumped time, when it did i had just downshifted and it bent every one of the intake valves just enough to cause no/very little compression. I obtained another head checked the valves, cleaned all surfaces, and re-assembled the motor with new head bolts, new head gasket, new timing chain, new tensioner, and new sprockets. The car has a fuel filter with less than 5k on it, and the fuel pump was strong when the indecent happened. I had a p0420 once on the car when I first got it, but it cleared up. Now upon start up it has a p0300, it idles really rough, but seems to clear up in higher RPMs. It runs kind of hot now but is full of coolant and the fan works. I'm sure this is something simple. I checked static timing, it's good, and I can't find any vacuum leaks of any kind. I'm an ex GM mechanic and ASE certified and for the first time since 2007 i don't have access to a scan tool that shows live data. Any help would be great.
Sounds like your timing is off.... I had this happen to me after doing my timing chain on my 1997 and it would misfire at idle, then when you got it over 3000 rpms it would clear up... But without actually seeing whats going on its hard to determine an exact cause
Had a similar problem on mine when my water pump went. Did you have the new head decked when you put it on if not then there is your problem most likely.
The LN2 is an interference engine, so when the chain jumped, it may have bent the valves. Or you may have a plug, coil or wire issue if you haven't checked already.