ive recently bought a mk4 golf off one of members from CGTI. its a 2000 ARZ, 148k miles and all in all it seems pretty good. i gave it a bit of a once over today because i could feel all wasnt well with the new acquisition. firstly the car had quite noticable lag, ie on par with an escort RS turbo from back in the day and a 20vt aint meant to be like that. so tonight i had 15-20 minutes, i had a quick dive into the engine bay as i had a few ideas, firstly either a big boost/vac leak or DV not sealing. i knew the rough principals behind the N249 (ecu controlling DV mechanisms) and decided id rather just have the DV controlled by vacuum. a couple snips and a new vac line later the dv is being controlled as nature intended (i will read more into it incase there are going to be side effects) then i jumped on the uber typical breather hose splitting causing a boost leak. sure enough that was code F but without a replacement i snipped that too and stuck a bolt in it. vac line to the fuel pressure reg wasnt the best so that was replaced with typical 3mm id black silicon + a shot of oil syringed into the FPR. immediately the car feels different (and improving with every mile, adaptation i suppose). now the torque responds as soon as you hear the turbo and once on boost properly it has a fair bit more shove than before. i recon the missing mpg will come back pretty fast too. any idea where the MAP sensor is on an ARZ? (it may be the same as an AUM i think) tomorrow ill test the DV to see if it does seal properly and then ill test the lines for the N75. currently my breather doesnt connect to my inlet manifold. due to a one way valve that only funcitons on closed throttle anyway, but the rest of the breather is still connected to the airbox. is this sufficient or do i really need to reinstate the OEM breather settup? injector seals are leaking boost too. is this a big issue? will i gain much by recifying that in your experience?