I have seen somebody install a low boost supercharger to an IS250 on stock internals. Which can be done, but you'll he stuck on low low boost due to non strengthening of the engine. From what i hear the IS250 is all aluminum block and head, which all aluminum block doesn't do well with boost unless it was cast from the manufacture designed for boost then that's different. But to boost it after the fact you will have to bore & sleeve the block with enforced stronger metal sleeves. And if the the IS250 has a floating deck then you have to look into block guards put in. Im not sure if the IS250 has a floating deck or not so yo u have to look into it. Also engine block bracing as well. Then lowering the compression with low compression pistons and rings and re-adjusting the piston ring clearance a little lose from stock i believe. A thicker head gasket can also drop compression as well. i could be wrong, but I'm sure somebody will correct me.
i mean you don't have to sleeve the block, it might be able to take the added boost as it is.
too my knowledge not sure if their are any boosting kits for the IS250. if their is great, but if not, their will be a lot of custom work to be done. expect your build to cost around 8 thousand bucks or maybe more when done most of that will go towards building your foundation to make everything boost ready. If your boosting low, like a few PSI from stock then your build cost won't be that much more like 5 thousand i guess.
MY IS is Boosted with imagination by Sesame Street Performance (lol)
HKS DLI ignition box, PHR alternator 230amp or 250amp peak idk, Walbro 255lph fuel pump, Brain Crower 264 cams, SRT Intake with RaceECU, Fidinza adjustment Cam-gear Exhaust set 0, Mishimoto Engine&Trans radiator+hoses, megan racing y-pipe, OEM FRS 4.10 rear Torsen LSD diff, greddy EVO2 cat-back, SSR type CRS wheels, Tokico Illumina 5-way shocks, Cusco blue swaybars and chassis stiffiners..... Doin that all motor build