Our delta kitchen faucet with the sprayer and faucet all in one started losing pressure 48hours ago and it is down to a trickle now. We have taken it all apart and can't find a blockage. Any ideas?

Point your water line into a bucket and turn the water on at the wall. If you get a good flow, we'll go back to the faucet. No kinks in the supply lines, right? The reason I ask is this was reminiscent of a recent problem where my friend could get hot water to the faucet, and it would slowly go down to a trickle. The problem was that the supply hose had a bit of a kink in it, and got choked off when the line got hot.
OK, good flow into the bucket. Sometimes the supply lines can delaminate, and choke the water off as well. Since you have a sprayer faucet combo, make sure that the flex hose that dispenses the water, and has the weight on it to retract the nozzle back up doesn't have a kink either. Remove the spray nozzle, and try the faucet, holding onto the hose. It's possible that the spray selector could have a problem, so check the spray head and diffuser. With the water on, push the sprayer button, and see if the problem might be there. Remove the aerator on the end of the sprayer, and check the screens for pluggage. My guess is that the issue is in the spray head.
Best regards, --W/D--