don't want to **** anyone off but this is not on a car,it's on my 95 Z71,has a 350 TBI and I'm getting upto 10* of retard under heavy acceleration,4-5* at half throttle(on scanner)I gave it a full tune up,plugs,wires,cap,rotor,filters,timing,removed Hypertech chip tom see if this was a problem it has a new Dynomax exhaust and low mileage,any suggestions would be great