Beetle csp High flow adapting header

[3crispies]

Apologies if in wrong section.
Want to use our stainless high flow (without pre heat) for a subaru swop. Question is can I weld new headers into original exhaust ports and blank of HX outlets or alter them somehow. Will this create issues with exhaust gases internally, wrong back pressures creating maybe lean running, is harmonics internally a thing. Reason for keeping is love the oem look and the sound of the Csp.
Cant afford a £1k on custom exhaust and most people conversions seem to throw any old silencer on headers with results, I am by no means too clued up on exhaust internals but I know our csp is full of wadding internally.

Again apologies and thanks.