First off locate the proper pulley to replace the idler wheel below the Alt and above the A/C Compressor,you will also need a shorter belt Gates #K060806 does the trick.

I used a tensioner pulley off of a 4.3L V6 truck engine from the wrecking yard.

Remove the old "smoothy"pulley.

Pull the white plastic cover cap back on the top heater hose line.

Use a file or a dremel tool to grind down the ridge on the aluminum housing being careful not to damage the heater hose connector.

I used a hand file and it took less than 5 minutes to get it done.

You can put the white cover back now.

Now you can install your new or used pulley,if your using the 4.3L pulley there is a small spacer that GM uses to make it universal as they use a smaller bolt on that application.

Discard the spacer you don't need it.

Now use your original bolt and tighten her up.

Re route your new belt and check to see if there is enough clearance for the belt going by the heater hose outlet.

Now fire it up and see if it rubs,its close but an 1/8 of an inch is plenty.

Now take her for a test spin and blow the doors off that mini van with your free 5 hp