Clogged cat will affect engine volume throughput, altering air fuel ratios etc. Really will be seen while running - no power on acceleration or pulling uphill. No knowledge on codes - probably one of the others on the site can help with that.

A bad cat will make the performace of the truck real bad (no power while driving, idle bad ect.). You would be going through alot of gas too. Maybe try to clean the mass air flow sensor. The mass air flow sensor regulates the amount of air fuel mixture. I know when I cleaned the mass air flow sensor and changed the o2 sensor my gas milage increased. How did the plugs look when you changed them. Did they look like the truck was running rich? They should look tan. I was told to use denso factory plugs due to the double prong for the electrode. When my starter was going in would not turn over like a dead spot when trying to start the truck.

I don't really have any performance issues.. Got 19MPG on the last highway trip.. That is with a pretty good load using the air for about half the trip.. The power is good and it idles fine, smooth as can be! If it started properly, I would have absolutely no problems with the truck! Once it starts, it runs like it is brand new (and I had one of these '95 T100's brand new.. leased it and learned my lesson!) So no hesitation, no power loss, idles smooth.. When I changed the plugs, I put factory plugs in it along with factory plug wires.. I just checked the old plugs and they look tan.. I checked my file and the guy did say he had a new Throttle Position Sensor put in and right after I got the truck, the check engine light came on with the code for that sensor so my mechanic just made an adjustment and the light never came back on with that code.. It came back on with the cat converter code but like I said, after the plugs and plug wires were changed, the light went out and has never come back on and it's been over a month ago.. I just don't get it but it is frustrating, especially when a buddy says "is this Toyota going to start?".. Can I clean the mass air flow sensor myself or does it need to go to Toyota? If I take it to Toyota, I would have to pay and would probably have them check the pressure in the fuel lines.. Just trying to not incur that expense.. I appreciate the help!

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.html

Here it tells you how to clean it . Advance Auto sells the cleaner.

http://www.4x4wire.com/forums/showf...p;amp;sb=5&o=365&fpart=1

Check this out too

I will clean the mass air flow sensor today and have that check valve on the fuel pump looked at tomorrow.. Maybe it is stuck in the open position when they replaced the fuel lines!

Thanks for the helpful posts, I'll report back!

Ive been having the same starting issue for the past few years on my 97 but mostly when outside temp is above 60 degrees. First thoughts were fuel pressure, checked for leaking pressure regulator adding excess fuel, new plugs, performed pressurized injector cleaning. no help, I'm getting an average 18mpg. One night I left the truck inside the shop at my work, so it would stay warm, then pulled the plugs before starting and found at least three of them smelled of excess fuel, slightly damp. My guess is that I have some leaking injectors, and due to the temp, only affects a warm start. I have not replaced any due to the $100 + expense. thinking about sending them out to be bench tested and cleaned. Hope that helps a bit , I could use some ideas too

Well, I'm back to report the latest.. I was pulling a pretty big load and the check engine light came back on.. Cat Converter again! Had that replaced along with both O2 sensors.. I understand it takes the computer a little while to adjust.. The O2 sensors were toast! Also asked the mechanic about the MAF sensor and he said he cleaned it when he changed the plugs.. The truck is still doing the extended cycle thing at startup, not sure if the computer will correct anything.. Had the truck out last night and once it's started, it runs like it is brand new.. so smooth! The mechanic did not think it was an issue with the check valve because every morning it fires right up.. He said if it was a check valve issue, the pressure had all night to bleed back and should do it every morning! So I have changed (or recently been changed )the plugs, plug wires, cat converter, O2 sensors, air filter, fuel pump, fuel filter, battery, cleaned the MAF sensor and it still wants to chug at startup.. Also, the gas mileage before I changed the O2 sensors was 18-19! Everything I changed needed changed so I haven't thrown money away but I can't believe this problem isn't solved yet! I haven't seafoamed the engine, is that next?

seafoam before plugs i believe, otherwise it may foul them.