147 Lack of power between 45 and 65mph
My 147 has a lack of power issue. The car seems fine in 1st, 2nd and 3rd gear. When motorway driving the car lacks power (struggles to accelerate) when put into 4th / 5th gear. When the car hits about 65/70mph the engine seems to get it's power back and accelerates normally. If the car slows down to 60mph, then it lacks power again, and struggles up to 70mph.
Also, on a 2 hour motorway drive at the weekend, I had to slow down to 50mph (because of roadworks), and the car lacked power as usual, but it began to knock / bang, from under the bonnet (seemed like the left side). Could this have been the air filter box moving about?
I pulled the car over, and everything looked fine under the bonnet. Set off again, and no knock / bang under the bonnet.
I have changed the spark plugs, air filter, run the car without the MAF (no change), but this hasn't fixed the problem.
Any help would be much appreciated.