i had a charge pipe blasted as it had a million layers of paint on it

how do i clean this, i tried running some engine cleaner through it but still not the best?

ive been told to use wd40 (loads of) to get all the stuff too stick too it then petrol and finish with a high pressure washer???

has anyone had this and sorted it and how...........

i really want too use it as its a fiesta rst one thats been modded to fit on my zetec and fits perfect, and will be a ball ache too do another and have the same problem after someone cuts/ machines and welds my other one?