On modern cars, like my '99 996, does the pre-cat O2 sensor affect mixture all through the rpm range? (Other than WOT)? Like most new engines, it has two sets of sensors, pre-cat and after. I've been told that the after-cat ones don't affect performance, they only monitor the cats. So it's the pre-cat ones I'm wondering about.
Car runs great but might be a little down on power/torque. It's the only one I've ever driven, so I would not know until a buddy drove it who has driven many and thought it was not at 100%. The car has super-high miles, (205k), but the motor is newer. (Unknown miles). I'm thinking that they re-used all of the exhaust parts and unfortunately I did not get records showing previous maintenance. It runs really well but I'd love to get a few more easy ponies out of it if they're sitting on the table, so to speak.
On a related note, we suspect that the cats might be original and not operating at peak efficiency. Any way to tell? There are no CEL lights on, car starts and runs flawlessly, etc..., but if they are original they are really old.
Before I spring for some low-mile cats and new O2 sensors, I thought I'd run it past you guys. I think that this is a generic question, IOW, if you have experience w/ some other modern car, please chime in. TIA as always!
