I need some help guys. 2001 s10 Blazer zr2 4.3. Was running find then started to run rough and missing. Quit on me had to get towed! The usually thought fuel pump but no 62 psi and held at 57-58 for a good 15 min. Pulled the dizzy cap off and found the problem. One of the screws that holds the rotor on had worked loose and then broke the rotor and when the screw came all the way out of course the rotor was flopping around so there goes the timing. Installed a new cap and rotor and it started right up and in the driveway it idled and revved up perfectly. Shut it off,buttoned everything up and took a test spin. Just out of the driveway it started to sputter wouldn't go over 10 mph and only about 1700 rpm. Babbied it back home and scanned it and got back two codes. PO 303 #3 misfire and a PO 101 mass air flow. Checked spark on #3 good. Cleaned MAF with MAF cleaner. It starts perfectly but still no power. Step on the gas it kind of shutters. Can the cat plug up that quickly? Help me out guys. Thanks in advance.

Thanks for the two responses. I’ll check those things tomorrow.
Keep the thoughts coming guys!!!!!!