ok, i just read throgh your thread and if the only thing u changed with the fuel tank then this is very odd, but heres some things to take into concideration.

If your fuel tank had any kinda leak in it, that changes your overall system fuel pressure, with will throw off your tune slightly.

If you have fuel, If you have spark, there are only two other things needed to make an engine run. They are Compression & Timming. You need to do a compression check to make sure that your smoke isn't because of bad rings / ring lands / ect.

I'd also check the timing while your at it, i know u didn't change anything but it's worth checking.

Then, apparently you don't have a wideband in the car or you would know what the fuel problem is if there is one. So what i'm going to have to say is, get your tuner to take a look at the car very soon, don't attempt to drive it like that.