I have heard only good thinks about Lucas products, although I have never used them. Which product are you looking at using?
The only "snake oil" products I have used are Sea Foam in various vehicle fuel systems with good results, and Marvel Mystery Oil, ironically in a Pinto in 1986. I have "cured" skipping/missing/stalling issues with Sea Foam in 1990's fuel injected vehicles. I was pleasantly surprised how well it worked. The Marvel Mystery Oil story is that my '77 Pinto sat for 6 months while I was out on a Navy deployment. When I got back I got it started but it had a slight knock in the engine. I drove it from the long term parking lot directly to the Navy Exchange, bought a can of Marvel Mystery Oil, dumped it in the crank case, then drove it. In 5 miles or less, the knock went away, and I drove the car for two more years. I don't know if it would have quieted down just by driving it, but it feel the Mystery Oil helped.