2NZ FE poor acceleration

[HaavardPYA]

Hi. I just bought an 2001 Yaris Verso 1,3 vvti. The acceleration is really bad and when i change gears on 50-100% throttle it jerks just when i release the clutch after shifting.

It has a bad exhaust, so can this be a problem coming from the two o2 sensors reading wrong values causing rich or lean fuel mixture? The yellow engine light also comes on after driving for about 20-30 minutes after resetting the ECU.

I have not had a chance to getting the car up on jack stands locating the leakage yet, but I will do it this weekend. Also going to clean the IAC, throttle body and MAF at the same time. The coolant level is at max in the expansion tank, but sometimes when cold, the coolant lamp comes on. OBD tool is allready ordered.

Something else you would recomend me to do at the same time?

best regards