I put an 08 5.3L and a 4L60E in my 67 C10 pickup. It runs great except for one annoying issue. Sometimes at a constant light throttle the RPM will raise and lower over and over by about 300 RPM and give a bank 1 and 2 lean code (P0171 and P0174). If I let off or get on the throttle the surging stops and it drives normally. I took a freeze frame of when the issue occurs and got the following:
Fuel sys 1 CL
Fuel sys 2 CL
Calc load 74.5%
ECT 92 deg C
STFT B1 1.6%
LTFT B1 29.7%
STFT B2 1.6%
LTFT B2 29.7%
MAP 78 KPA
RPM 1924
Speed 54 Km/H
IAT 45 deg C
MAF 55.39 g/s
TPS 40%
Run time 443 sec
Command Evap 100%
Warm up DTC clear 9
Dist 115 km
CAT1 420 deg C
CAT2 420 deg C
ECU volts 12.6
Load value 54%
EQ ratio .999
Rel TPS 25.5%
Ambient 28 deg C
TPS B 39.6
ACC pedal D 34.5%
ACC pedal E 17.3%
Command TAC 37.3%
Evap up 1875 Pa

Any help would be greatly appreciated. John from Speartech thinks that it may be that I have an E85 tune on a non-E85 engine. Is this a possible reason for this issue?

 

Your long term trims are locked at nearly 30% additive. I'd say that at a glance, it looks like it needs to be tuned.

 

Would that be the case with the E85 tune?

 

Anyone have any more info on this. Is it worth sending the ECM back to Speartech to change the tune?