What size engine is in the van? The 8th digit on the vin would helpful as well. If it is a 5.7L, then Fast355 has you covered. You will need some form of scan tool to begin with.

You have room to cheat a little without a chip. Advancing base timing by turning the distributor until your IAC valve reading on the scan tool is about 3-4 counts on a warmed up engine. Advancing timing this way has a price, the idle will destabilize a bit, but not too badly. That is the "EL-CHEAPO" amateur mod. heh. Worked on my truck's v6. Runs like a v8, that was enough for me at the time.