Get the fault codes scanned and take a look at the values of the engine management. I'm pretty sure this generation of the 119 motor has coil overs, so the plug wires are part of the engine harness. You may want to check the sparkplug boots though. For fun, take a look at the main vacuum line from the brake booster to the intake to see if it's broken. That could cause a massive vacuum leak that would surely feel like a dead miss at idle...