By sayng its the worst engine/car lexus ever made is cleary an exaggeration and not true. First gen is200 is worse.
Head gasket issue was fixed free of charge by factory extended warranty 180k km.
Diesel engine needs more maintenance but this is the same on all makes. Every make has its problems, Audi/VW have a weak turbo chargers, engine eats oil/rings worn out/timing chains, MB have issues with injector washers burning in and BMW is overall least realible out there.
IS250 bulletproof, really??? VVTI cam gear fail? Carbon buildup? Burning oil like crazy after 100k km, piston rings seized up, that is a known issue - full engine rebuild. Fuel pumps going out and are very pricy to replase, auto boxes not in their first youth and failing. I would say its not any better than is220, probably even worse.
And what about fuel consumtion? if you drive mostly in urban areas is250 takes twice as much as is220. Not to mention is250 is slow as f**k.
EGR needs cleaning once a year/or every 20k km, it takes half an hour and a can of brake cleaner not £500, what a joke. DPF does not need any maintenace, it takes care for itself. When force regeneration is needed then there is something wrong with injectors.
Where in hell did you take that remapped/gutted engine would going to grenade itself? Did you see that happen or this is another exaggeration because you clearly just hate any diesel out there. I have seen only BMW engine to explode but that was just chain worn out and owner pushed it to the max.
ECU can be remapped with EGR/DPF still in place and working fine, this is the recommended route. Cutting DPF is already last move when its clogged and does not work. I personally would never do that, engine starts to smoke and smell very bad + illegal etc.
I have been driving this car for over 10 years, remaped last 4. Only regret is that I did not remap it sooner. It feels truly like different car, but it wasnt bad before either. Also gears feel better, a known issue with manual models.
Never has there been a EGR/DPF/injector related issue. Ofcourse the head gasket. I replaced that and out of my pocket because warranty was over but thats ok. Used and checked engine costs about 1k if that ever needs to be changed. Or use swap from other models/makes.
I have other cars I use daily, also turbo diesels. Audi a6 - that has lot of work being done, new turbo, timing chains, injector, DPF cleaning ect, all normal diesel issues. This one is not remaped.
Ford van - modified intake and remaped from 75hp to 110hp since new and NO engine/diesel related issues for 10 years.