Trying to figure out where to start. I have read 20 pages of posts here so far and have some ideas what to check first but was curious if this board is still current. (don't see too many posts for 2016). I helped my boy put a KLDE into a 94 gs with the K8. a while back. Starts and runs fine , slight miss but nothing horrendous, but it just craps black smoke and soot out of tail pipe when revved. I saw on here how to read codes so I will check that tomorrow. As far as compression I only did a dry test and got an average of 165 over 6 holes.
When we installed the newer engine I bought him a disty that was for the 93 DE engine we installed but the engine wouldn't start at all , We put the 94 K8 disty in and the car fired right up.
So far I can see that there is an exhaust manifold stud broken where the exhaust pipe bolts up and I can see it was /is leaking. I'm hoping this is causing o2 sensor to read lean and send too much fuel. I cant see any vacuum lines we missed. like I said the car is driveable other than the absolute crap gas mileage and the black stain on the driveway (or anywhere its parked running for 5 minutes)
Any help would be appreciated..... He wont let me bolt on an Edelbrock 650 from my mud truck

Thanks