I have a '89 civic dx converted over to a '94 D16Z6 using a '91 Si intake, ECU, and Distributor and a MSD RPM switch to activate the VTEC. Ever since the swap the car has run very rich (black soot in exhaust) but I have noticed something really odd. When accelerating, it stumbles slightly and sounds like it is pinging until the VTEC switches on at 4400 RPM and then it smooths out and accelerates well (except for accompanying black smoke). This seems backwards to me - if it is pinging shouldn't it get worse on the big cam?? Or am I mistaking something else for pinging and it is really running so rich that it can barely go on the low cam? It has the stock ignition and stock ignition timing, I was thinking of going to MSD modified cap with external coil but don't know if this is a worthwhile mod. Any suggestions are appreciated.