When you say lambda sensor, do you mean the oxygen sensor?
Have you tried checking or adjusting your air/fuel mixture? Also known as lambda/on-off ratio.....
If you have a lower chamber pressure leak (in fuel distributor) then your lamda reading will fluctuate pretty wildly. You need a multimeter with duty cycle function to check this. Sears sells a good one for $30.
You can also check your fuel system pressure and make sure it is within specs. Do you have any warm start problems? Have you replaced your original overvoltage protection relay?
Good Luck and keep us up to date... we're here to help
