I put a boost guage on the other day. My question is at how many psi of boost is the waste gate suppossed to open on a stock 98.5 24v. I see the guage drop when it hits 18 psi

 

18 psi sounds about right , or maybe a little tiny bit low, is your truck stock? What are your EGT's, you might not need more boost than that right now , if the truck is stock a couple more psi won't make much difference.

Here are the specs according to dodgeram.org:

Maximum Boost for stock Rams:
94+ 160, 175, 180 HP 15-18 PSI
96+ 215 HP 21-23 PSI
1998+ ISB 19-22 PSI

 

21psi is the average