Freinds truck got a problem

[tractor8]

My freind has a 89'GMC K1500 w/ 5.7. The check engine light comes on when it gets good and hot. Pulled the codes and got a Electronic Spark Control and EGR system malfunction. The truck doesn't seem to have the power it should and sometimes back fires through the intake when you get back on the gas after coasting. It also sometimes stutters on acceleration from a stop. It has been converted to true duals with flowmasters and no cats (SHHHHHH) Does anybody know what could be wrong, the EGR seems to check out O.K. but it could still be the problem.