Paradox51483

Recently my motor has been rebuilt and broken in. When it was rebuilt, RC Engineering 750cc secondary injectors were put in, the wastegate was ported and welded open & street port on the intake. After it was broken in we added the Greddy Profec B spec 2 boost controller, S-AFCII & Walbro 255lph. Now heres the problem. After 3 hours of dyno tuning and $7500 later the car still isnt running right. And besides it only put out 205rwhp and 201 Torque? What's up with that? Cruising with maybe 50% throttle pushed up to 3K RPM daily driving, the car stutters and stumbles. When I hit boost the car jumps around and stumbles bad then pulls through and when you let off the gas the car completely shuts off. Now, its an 88 so it has instant 100% throttle instead of a grid type like the S5. We have cut back the 750's 30% and the low end is as lean as possible. They also tried to tell me that the Boost Sensor was bad. But I think its fine and that the car just isnt tuned right. What do you guys think?

SureShot

First, You may be better off to tap the pressure signal to on to the gray THR wire to select between the high & low maps.

Next check the AFM's AIR readout on the S-AFC.
Is it ramping up smoothly? If not, the ECU will give fuel cuts.
Is it hitting 100% too early? If so the S-AFC's corrections above that point must be smooth, or the ECU will give fuel cuts.

I'm temporarily running on a Mazda 929 AFM until I can get a good replacement. It's a pain to tune, but at least it's on the road.

Paradox51483

Well lets see. At 50% throttle the Afl setting is reading about 4%+ and thats about it.

SureShot

Next try adding more fuel correction to the high map at the RPM's where you get the mis-firing.

I envy your Profec B.
But wait, You said the waste gate is welded open?
I assumed the Profec controls the waste gate.

(I'm currently troubleshooting a high power lean out mis-fire, but it seems to be a fuel pressure problem.)