Freelander 1 TD4 Lack of power, split hose mystery?

A bit of a strange one. I noticed the other day the short straight hose ( approx 100mm ) on the top front of the engine had split for about 40% of its circumference. Not a problem, so i got one off ebay. Now here is the mystery. When i put the new hose on the car looses power. It takes forever to get to about 2.6K revs and then takes off again.
I put the split hose back on and all is normal? Im baffled. Im presuming this short hose is an inter cooler hose? Any ideas?

Is it this hose?
If so, it should go better when is not split as boost will be getting to the engine.
It could be worth looking at the live data so you can check the boost pressure the EDC is seeing.
I'm thinking along the lines that the MAP sensor is blocked.

Thanks for the reply, that is the hose im talking about.Its a 56 Reg TD4. I will give the MAP sensor a clean tomorrow if i can find it?
Edit, just had a search and found a pic of its location. I will try and remove it / clean it tomorrow and report back.

I have given the car a full service. Also taken off the inlet manifold and cleaned it all out as well as giving the MAP sensor a good dose of contact cleaner. Still the same unfortunately. I have ordered a new MAP sensor and will fit it when it arrives. Failing that i will have to find someone to do some live readings. I will update after i have changed the MAP sensor.

Quick update on this one. I decided to have another fiddle today. Put the new pipe back on and disconnected the MAF sensor. All is well. Looks like the MAF sensor is no good. The split in the pipe must have been compensating somehow? I will run like that till the MAF arrives