89 d50 idle question

Hi, I'm new to the forum and I have a 89 power ram d50 4wd with the 2.6 and mikuni carb. My question is that it idles around 1300 rpm's and I would like to lower the idle a little and I'm short on cash right now so a manual will have to wait . I'm very mechanically inclined so if any one has a suggestion please feel free to help . thanks!

Cheers