I currently have a 6 slit diffused downstem. Should I get a multi-arm perced precooler or a 6 arm diffused downstem or a showerhead? Which would have the greatest impact?
I'd say upgrade the downstem first. Although an A/C would drastically change the way your tube hits, more so than a downstem, IMO.
Ac first, then downstem, since u already have a diffused downstem the ashcatcher is all u need. Showerheads are worth every penny, same with luke wilson stems. Also be careful on buying an ac, most are more trouble than good. We could help u greatly if we knew wat kind of bong u got. Some downstems perform better than others in differant styles of bongs.