I have a 94 z28 thats stumbling on acceleration so i probly need to replace the opti. a mechanic friend of mine said it may have carbon build up in the rotor or something. I went on ebay and found ac delco optis for around $290 and MSD cap and rotor for $150. Which would be the better buy?
Also when it comes to replacing it do i have to take the water pump off? or can i take off the pulley thats right under it?

 

My car was also stumbling and soon after that, the opti died out completely. I personally would replace the whole opti to prevent problems in the near future. I went with the new accel opti and so far it does it's job great. I paid $300 for it from summit but I think northern auto parts sells it for $200 now but I'm not sure if they make it for your year. If they do, that may be a good way to go. And to answer your question, yes you do have to remove the water pump and also the crank pulley. It's not really hard. It's just time consuming.