Gambit, the end section was flared on the old part I removed. The new section is not flared, it is the same bore as the end of the downpipe. The Haynes manual illustrates the use of a sleeve, however, I thought this was only for early GTi's and not later models. Has anyone recently fitted a new front box to the downpipe? It seems my old front box may have been manufactured to avoid the use of a sleeve.