The L31 is ancient technology as most anybody who tries to get power out of one does an 0411 PCM swap. Virtually nothing from the newer tune tables will easily translate over as the black box l31 PCM is only a 256mb PCM. There's a few people who tune them, but not many as most abandon them for the 0411 and an 02 van tune.
Search 0411 pcm swap on google, you'll find lots of pages regarding it. The pins in the black box ecm plug get removed, and put into an 0411 pcm plug. The tricky part is getting the correct diagrams for the l31 pcm as GM made small wiring changes each year on them. Once you obtain the correct diagrams, you just swap the pins over 1 at a time. Flash the 0411 pcm with an 02 van tune modified accordingly, and away you go. The only issue I know of is 98+ also require a fuel guage buffer or interface wired in to make the stock fuel guage work.
The fuel guage is 98+ as 96-97 was still hard wired. I know efilive has never seen fit to add in the fuel guage tables despite requests for it. There are other ways around the fuel guage issue for 98+.get on any gmt400 forum and search for member lextech he has all the diagrams needed to make the re-pining easy. the bulk of it only takes an hour. There is an option in HP tuners for PWM fuel gage to make the gauge work properly. (my gauge was bad from the get go so I have not confirmed this)