Diesel Injectors

Halo! I have a BMW X5 diesel 2005. My turbo was replaced and the company advised me that the injectors needed replacement as well (139000km). Since new ones were totally out of my budget, i had them refurbished with new tips as well. now the problem i have is that since the injectors were refitted, diesel is bubling up from the bottom of 3 injectors. swapping 2 around somewhat cured it but there is a constant diesel smell from leakage at the injectors. torquing them down more also doesnt help. Please help since i dont know which way to cure this now!?

Are there any type of seals on the injectors that may need replaced? Check realoem.com for diagrams/parts info.
I just looked and there are gasket rings and O rings shown. These might be a good place to start.