Haidar bhai I haven't changed the shocks yet cos I've been quite busy lately but the guy from ironman said it shouldn't be an issue. My springs are also fairly new as I've only covered 12k up till now. Lets see how this change goes, I always have the option to go back to OEM shocks.
I did a bit of research on shocks. The OEM shocks in Fortuner are locally made in some factory near hub and they're single tube shocks, while Nitrogas is a new technology and they're a twin tube shocks. Handling, Braking and Cornering should defiantly improve but how it takes the bumps needs to be checked. I talked to a guy who's been using ironman shocks since 2018 and he's super impressed with them, in fact he said he changed the shocks right after he got his delivery for Legender.
Lets see how it goes, just need to fetch sometime and get them changed