An ongoing issue

Hello all. Hoping I can get some solutions to a problem I have. May have been covered before. Apologies if so. I have found relevant information in the Fabia section but was hoping for a bit more information about the rapid. Like location of sensors for example.

Car - 1.6 spaceback. Diesel

Issue- Fault code PO236. Loss of car boost peformance. Management lights constantly up and car is generally very poor at accelerating, especially in lower gears. Definately not as efficient as it was. I have taken it to the local garage and they don't seem to know what's wrong with it. I don't really want to take it back to the dealer if it's an easy fix I could do myself. And I worry they will charge extortionately.

I read in the Fabia section that replacing the map sensor/ boost sensor is a very likely fix. Does anyone know its location? 

Another thing is sometimes I get the glow plug warning flash when turning the ignition on. When I restart the warning disappears. Not sure if this could be linked or a separate problem?

Any help would be greatly appreciated. I'm a bit of a DIY kind of guy and always keen to try fixing it myself. Cheers