Power and exhaust sound issues
 

Hey all. I am in dire need of help. My Is300 has about 118k miles on in and has never had any running issues until recently. About 2 weeks ago I was driving the car and literary out of nowhere I felt a substantial low end power loss. I don't know if this happened at the same time but I noticed my exhaust was quiet a bit quieter almost as much as stock. Keep in mind my modification. I'm confused on what to do.

Some are suggesting bad head gasket but my car has never over heated, oil has never burned or gone down in level, Never had any misfires, Oil is amber color like normal oil, No steam in my exhaust.

I am confused because bad ignition would result in some kind of misfire or stuttering to my knowledge.....And the problem started literally out of know where. Spark plugs have been changed with in the last few months and ran great up until now.

Mods:
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Toyomoto Header + Y pipe, 18inch resignator and magna flow muffler ( No Cats)
AEM Intake.
Suspension stuff and a lighter flywheel and better clutch.

Please help

Any check engine lights, past or present???

My first guess would relate to the throttle body failing, but that is solely a guess based on the basic symptoms...

What were you doing when the power loss became evident? Just cruising, accelerating???

I have a CEL for Bank2 Sensor2 due to my headers and no cats. I just cleared the code with my phone and then the power seems to have dropped off at low end. Felt like i just had a massive exhaust leak. I was just cruising, Honestly i take very good car of my car, no racing just some fast corners every now and again.