Bluey smoke and exhaust changes sound

[gover87]

I have a 2006 535d
Ive done a back box delete and ever since the car drives fine untill i boot it, then the exhaust note goes very deep and i get bluey grey smoke from exhaust untill it decides to go bk to the normal sound and without any smoke, thinking its fuel related as its not using any oil (that i can tell) anyone got any ideas? Been told injector seals so ive got them to try over weekend

[TOGA]

Maybe check if there`s no leak from coolent into engine oil. This will also cause a blue-ish color to the exhaust. But again as you mention, it goes away when to "normal" sound. Do this box interfere with fuel mix?

[gover87]

No mate just deleted back box