P1521 is clutch sensor, the clutch peddle probably isn't returning to the top, usually because the self adjuster has jammed or gone to the end of its travel.
Faulty MAF will cause your power issue, but only replace with a genuine VDO unit. The cheap ones go faulty quickly. The EGR valve might also be leaking, best to blank it at the inlet elbow.
Faulty MAF will cause your power issue, but only replace with a genuine VDO unit. The cheap ones go faulty quickly. The EGR valve might also be leaking, best to blank it at the inlet elbow.