2008 Scion xB is my daily driver but occasionally load it up with about 900-1000 pounds for a job I do and I'm another 220ish. I'd like to keep it looking normal but able to handle the weight a little better. I would not mind a little stiffer ride but not too stiff. Any ideas? Right now the budget is a little tight and I'd mostly be interested in what can be done to just the back. I do not want it lowered.

 

Air Lift helper bags work great and are adjustable. I used them for years on my Odyssey for carrying heavy loads.

https://www.airliftcompany.com/vehicles/scion/xb/2008/

 

Max cargo weight is 850 lbs, including passengers. Time to remove unnecessary interior (free). Getting stiffer or higher springs on just the rear will change the handling. I would get a carbon fiber hood and tailgate ($$$).

 

Yes, I remember air lift shocks running on my dad's station wagon pulling a 23T+ trailer back in Flintstone's times. Greg S may have an economical idea because carbon fiber is mucho dineros...
Else, see if you can find someone that will sell you lightly used TRD springs (10% stiffer but only ~1.5" lower front & rear) because they wanted to slam their xB more. Lower COG = less sway in corners without additional (but good!) braces purchase. I'm running 225/40/18x8.5+35 and have no rubbing loaded with 5 adults

 

keep in mind quite a few guys are having rear wheel bearing issues. beefing up the suspension for additional weigh capacity will seriously shorten there life span. there is about 50 pounds of spare tire and stuff in the back of the XB2. also adds quite a bit of extra room. and noise. pulling the rear seat shaves just shy of 10 more pounds. gutting the rear 1/2 interior of seat belts, seat, trim, spare, carpet should shave about 100 pounds out of the box.