I’ve always been told if you have a miss under power it’s the spark plugs. If you have a miss at idle it’s plug wires. Does this hold true to a 98 throttle body Chevy? I don’t have a constant miss only intermittently at idle.
It’s a spider injection set up with only 2 injectors and 8 poppets. The pressure regulator is under the intake. A miss fire at idle and not while under load is not likely to be a fuel problem. But I’m willing to bet there’s a misfire under a load but you can’t tell. These systems require 60-66 psi and no less. The 5.7 vortec plugs are specific and need to be gapped 60 thousands. But there’s a common issue with the plastic bodied distributor wearing the gear out and the distributor floating around loose. Check to see if it will move around. If you have access to a scanner with live feed check the cam retard at idle. Has to be at zero +-2. It will miss fire if not. This engine has miss fire issues across the board. And all of them are simple to track and diagnose without throwing parts at it. A few simple upgrades will eliminate most of them and give you more hp and better fuel economy. I’ve done the distributor and upgraded to multi port fuel injection for 600 or less. It’s simple plug and play and eliminates several common issues. The difference is night and day. 97 and up also had passlock security issues and all the way up to 2003 the ignition switch control module’s in the steering column will send low voltage also causing miss fires.
