I have used Seafoam in many applications. Mostly sucked in through the main vac line at the brake-booster. Pouring it in the crank case will help remove buildup and varnish. The smoking comes only when you suck it into the head though. I have noticed a vast difference in throttle response after...
I removed the OEM dash speakers. With tin snips I cut holes in the metal speaker cover big enough for to set a set of PB 200 watt 1" titanium dome speakers, with crossover included. Wired em to the orig. wires. Sewed her back up and it sound awesome. I also have an aftermarket JVC head unit JVC...