Sprint booster, yeah I think thats what the previous owner said it was as well. As for any clunking sound I only seem to get it when letting off the gas shifting into second, rarely third. I shift in first around 2000, second about 2500-3000, Booster off it does it as well. This is a new learning curve with this car for me.

it also has a reprogrammed ECM, I'm still learning about the car.

Klunk is only when I shift up then depress the clutch maybe a bit fast, though I don't want to ride it . Its more sensitive to grab then I am used to. That and maybe not enough gas. little aggravating in stop an go traffic in the city .