[chittychittybangbang]

You are getting limp mode. Here's how to fix it: http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm First scan for error codes and do the tests to narrow down the source. It could be many things and without more details I could only make a total guess. Go step by step and follow the article to narrow it down. First scan for error codes, many auto parts stores will do this for free.

 

[chittychittybangbang]

Hissing could be a major boost leak. The hose clips can wear and pop out. It could also be a loose EGR hose. Check out the article and do more tests.

Most likely is a cracked vacuum line.