it sounds like the blue temp sensor again, check wiring loom again, i bought a new temp sensor and mine ran exactly how your describing yours running now, it struggled firing up, misfired and coughed black soot out of exhaust, i put my old sensor back in and it ran fine, the ones you buy from gsf aren'e guarenteed to work, they may be broke when bought.(heard of this problem before), if your proper stuck phone ace tune in sheffield, he's pretty clued up on old school cars. he might get it running a little better than it is at the moment and get you to ud. don't trust his fault code reader tho, its totally inaccurate. 01709 710 888, he charges around £35