I've been fighting this restricted performance for awhile now. Had it into my friends at Tires plus but they haven't been able to figure anything out. Last week they cleared the codes, today I drove down the interstate, about 75 miles, got on it a number of times (kicked in the super charger) and it ran perfect. Did some shopping, let it sit an hour, got back on the interstate and within 5 minutes got the orange engine light and restricted performance message, yet i was cruising at 75mph. So I decided to punch it and that's when the engine felt like it was shutting down. Speed went down to around 50 and I could do nothing about it, i kept tapping the gas, not luck until 50 when it started bucking and then picked back up to 70-75 and ran fine (message and light still on). So I ran about 20 minutes and punched it again, same thing, speed dropped to 50 then bucked a couple times, then back up to 75 no problem. Then all of a sudden the reduced performance message went away, orange engine light still on, but now i could punch it with no problem. Took the car to Tires plus checked the codes, got a P0171 and PO174 (right and left lean codes) and a P1000. Cleared the codes, ran about 30 miles around town, no issue. Any ideas?

 

Post is in wrong forum, should be in the X200 S-Type forum.

The DTCs P0171 and P0174 mean there is a vacuum leak, which is most likely causing misfire(s). If the MIL is on, the vehicle has gone through two restart cycles and the DTCs are reset. Clearing them is not the answer because the monitors will now need to reset.

Check for vacuum leaks around the manifold and the air plenum from the air cleaner through the MAF. Pay particular attention to the sealing ring around the MAF as they can leak unmetered air and cause a lean condition on both banks.

Through the OBD port, check the STFTs and LTFTs and post the results on the S-Type forum.

Under no circumstances operate the vehicle under conditions that cause the MIL to flash as catalyst damage is occurring.

 

Don't. Instead, fix the fault they hint at.

There is no "yet".

Yes, it's trying not to let you destroy the engine.

Ouch. A bit like kicking a horse that went lame.

You have one or more faults, work through the likely causes of those codes as described in detail in the codes PDF / workshop manual - free downloads. (Search will get you lots of details.)

Don't continue as you describe or it'll get expensive in parts.

If this is beyond you or unattractive, find a competent tech and soon.