An option for my vehicle

Hello, I have struggled for the past years searching for tuners and software to tune my 2006 Lexus GS300 2WD. So far I found one Tuner in a different country who was able to tune my car, he increased my RPM to 7000, also inactivated my o2 since I don't have catalytic converter. I'm not sure if disable the o2 is a good thing since it calculate the AFR? i noticed maybe 5% of increase after the tune and I have a monitor display showing me the Torque and HP along with other a few things but I notice the Torque Increases at 4000RPM then drops down at from about 6-7, I believe I got a bad tune, also he used PCMTUNER software. what's your opinion on that?

Thank you!

I may be mis-interpretating your question, but it reads like exactly what would be expected.

It is normal for the torque to drop off after the peak of the curve, and often quite steeply at maximum rpm. This may not have shown up as much with the original RPM limit but because you've extended it beyond the OEM point it may be more obvious. If the engine is mechanically strong enough for the abuse, it's possible to have the torque drop to a point where it's so low the vehicle can be held in a lower gear and it will simply not give any further speed increase.

Merely increasing the rpm without other changes will make no difference - it will actually reduce overall performance through the gears if the higher limit is sued as power may drop to lower than the level in the next gear.

Even with OEM vehicles, while it is usually best to rev to the "red line", this is not always the case - especially in the higher gears and/or close ratio gearboxes, and knowing the power/torque curves and gearing one can calculate the optimum shift points.

I do agree, though, that disabling the Os sensor could be questionable, unless it was the only way to get the enrichment for the lambda/AFR he wanted for the 'tune".

I can't comment on the software, or how good/bad the actual tune was, as I'm unfamiliar with either.