when you have your throtle body off look down into the intake manifold to see if any oil has pooled up in the bottom of there these engines are notorious for the plenum gasket going bad.
also i recently removed my catalytic converter and man did it help out alot, plus it sounds great now too.

 

When you take off the trottle body don't forget to clean the IAC solenoid and set the TPS between .7 and .75 volts that will wake up your "D". My heater core went out at 120k. Bosch platinums suck for "D"s since you are new to your "D" you will think they are the best thing going. I am going to tell you search the forums and learn. If you have a Question this site can answer it. Bosch will work good for a little while but in the long run the foul out quick.