ECU/Lambda situation (bit long)

[GDBN]

Hi ... see if I can explain this simply.
My cab is from Sept 86. Standard 325i. Imported from Spain through Germany here to Denmark. In Germany (was there about 10 days I think) the car was fitted with a new exhaust. Local laws and import duties here are ridiculous, so to reduce the import duty (185% on new cars then add 25% vat !!!) the car was fitted with a cat. My registration document says "environmentally friendly" - which means that according to danish law the car must always have a cat - especially for the mot.
But blow that - always wanted a decent exhaust so I bought a new Supersprint back box and then got the standard BMW replacement down pipes and centre box (made by Eberspacher). Wow what a sound.
BUT - I had to take out the lambda. I don't know if it was because it was all new but the exhaust fumes smelled a lot more of petrol.
Did the ECU switch to emergency mode without the lambda ?
Can it ?? As it's an old ecu (0261 200 703) with a 24 pin chip (ends in 73-1577)
Have spoken to Sal and Ant some time ago - they said there's nothing you can do with the ecu ie. chipping.
So for now the cat is back on (still with the Supersprint) and the car sounds crap again and definately isn't as lively (that's why I prefer dogs).
SO - would an ecu from 86 not need a new chip to accept the lambda ?
And if not by unplugging the lambda would the fuelling level change?
Sorry it's so long and hope it makes sense,

G

[Brianmoooore]

Simplest solution would be to weld on a M18 nut and fit a 4 wire lambda again. I fit them to the inner downpipe just above the roll bar mount.