Has anyone removed the cats in the 1st gen, and does it require a tune after? I live in the country in an area with high tall grasses, and run catless on most of my vehicles due to the fire hazard. Most of my vehicles are older than this though, so not sure if it would work here.

 

Let me answer this as I recently parted with my RX300 after almost 18 years (I will let you all know soon the whole story, but am so super busy with work). I stayed in the Lexus family though if you see my signature, also will explain that decision on the CT200h later.

I can tell you that doing this, putting aside legal reasons for a second, will yield loss of MPG and power. There was a brief period of time in Mexico between some repairs on the pre-cats that I had the main cat underneath that I was catless, It was not a pleasant experience in terms of noise either. In order to gain benefit, that RX300 would have to be putting out major hp, turbo, supercharger, nitrous, bascially forced induction. You also run the risk when completely catless of burning out exhaust valves because it essentially becomes one giant leak on a non-forced induction system.

Given the circumstances where I lived and no Lexus support there (Toyota existed thoguh), what I did given damage that I had with my RX300 was remove the two precats that are on the front and back of the engine. I can tell you that I fondly remember the manual transmission 1st generation Toyota Solara, which had a variant of our 1MZFE engine did not have precats, just a main cat underneath and would pass even the most stringent emissions tests in California. I also replaced twice going from one size Maganaflow to a larger Magnaflow main cat and passed twice the Mexico City emissions test (if you wanted to drive every day there, even foreign-plated cars were not immune to the hoy no circula or day you don't drive restrictions). The vehicle actually got better emissions figures with the one main Magnaflow cat than the original cat and two-precats. I actually had bad gas down there kill the cat and the two-precats. Their gas has much improved especially in being lower in sulfur. Mexico City used to have special vehicles sit at entrances to the city that would actually measure vehicles as they went by to see if they emitted too much pollution. I don't remember all the science involved, but it was extremely on point from some engineer friends of mine. I went by these plenty of times and never an issue.

So that's the mechanical answer above that should give you some pause before I even start bringing up legal reasons.

 

Could it be possible to have someone fabricate a heat shield on your
cats and exhaust that hangs low enought to hit the grass?