and its deffo not able to be done on a standard set up? standard manifold like....or will this cause something to blow up at around 150 bhp?
pics to follow later on the turbo
You referring to inlet or exhaust manifold now?
Inlet manifold as standard has one major flaw - it has enough flow for most people's needs, but it does nothing to help divide the airflow evenly accross all cylinders. If you look at any racing cars or well built street turbo cars, this will always be one key concern when designing manifolds. Not only does even airflow improve power, but crucially, it makes a big difference to reliability.
Exhaust manifold as it is on a 1.6 TD or 1.9 TD, is not the worst there is, but after 150 hp or so it will become a bottle neck. Of course, many people end up ditching it for a different reason, namely for the very rare turbo flange that won't allow many turbo upgrade options without adapter flanges, which can be tricky. BTW, good cast turbo manifolds with either T3 or T25 flange can be had for $150 on eBay.