Q&A

First and foremost, check the codes for the Check Engine Light.

see this article http://repairpal.com/check-engine-light

then repair your car based on what the codes tell you. And yes, the 'OptiSpark' system needs to be replaced every 90-100k and it is a really expensive job. it often gets ruined by the water pump beginning to leak, not a great design.

Hey, thanks for the compliments!
If the check engine light is on, there will be codes stored in the engine control module, if you can get these codes and post them we can give you more relevant information.
Thanks!

An optispark problem is a very costly one to tackle. First off, you need to go get your SS professionaly diagnosed, I spent hundreds of dollars chasing the problem in my SS. I just replaced my Opti and you should only use GM replacement parts, noone does the Opti better than GM (PERIOD). You can pick up a GM (AC DELCO) opti from amazon.com for $300 dollars plus shipping and it will take about 5 days to get. I opted to go to Advanced Auto Parts and I picked one up same day for $461 plus got back $35 for the core. If you have the time, I didn't, get it somewhere online for around $300.

If you are doing the opti you might as well do the ignition coil, MSD is about $50, new wires, MSD is around $100, and you would be STUPID to not replace your water pump, it HAS to come off, another $100, new plugs, use Delco Platinum Pros they work best PERIOD. If you do it at a reputable shop they'll probably charge about $500 in labor.

I kept getting a strong gas odor in my car and it kept popping the check engine light when cold and Cylinder 1 misfire or Random Multiple Cylinder misfire were the codes pulled. The car ran horrible until it totally warmed up, then it seemed to run just fine. It took many years until it ran so horrible that I broke down and replaced the Opti but my car runs like a new car again and I'm very happy. If you decide to try this yourself, buy a GM Service Manual for your Impala and I'd recommend torqueing everything to make sure you get it right the first time.

Good luck.