If you have the nivo's on the rear a saggy rear end is a common problem.
I carry a lot of load in mine and sometimes tow. The rear used to sag a lot but now with the coilovers on it takes very heavy loads well. My current V90 is the non nivo type and that was also saggy on the rear so I popped coilovers on that too.
https://www.classicswede.co.uk/Coilo...5_4319649.aspx