97 ECSB Stuttering after morning crank up

[97Layzboy]

Hey guys so i was having issues after installing a set of headers. Did an EGR delete kit and was told to have the ecm tuned (still havent done that yet). I replaced TPM sensor and IAC valve. It was slightly stuttering here and there but this morning i got in and headed down the road and it was stuttering and idling real bad. Weh ni was giving it gas, it would stutter real bad like it was trying to get power but it would never come out of it, and then i heard a slight "thunking" noise that sounded like under the truck. It wasnt constant but i could not determine what it really was. Any ideas on what i could check out? After work i am going to look it over. Im thinking its either electrical or gas related. I never did change out a fuel filter so maybe that could be a fix too? Let me knwo what you guys think. Thanks.