in neutral, rev the engine a little, then once it quiets down, it has a slight grind sound..... whats going on..???

 

any other symptoms?

 

no, thats all i've noticed. i just got the car back. i had to have stainless steel cats welded onto it for it to pass inspection. if i notice anything else i'll let you know..... i'll try changing the oil tomorrow. whats the best oil to use in my z???

 

The best oil to use would be the best oil you can afford. Mobil one is popular. Synthetic or semi-synthetic is what most ppl will recommend for a high performance engine either way ya go. But I think that timely oil changes does more for the life of your car than the particlar brand or type.
Since you just had the exhaust worked on...... Check the heat shields. They might not of tightened them all. Them vibrating MIGHT be the 'grinding' you hear. Just a thought.

 

thanks for the suggestions, it's raining something awful here today, so the z is gonna have to stay in today. i'll have to look into all this tomorrow. i'll let you know what i find. thanks again.