Okay so im stumped on this one. 1999 Lx Sedan 5 speed, 196k miles, just did a tune up on it, it was running good for the first couple days but now its like this damn thing is in limp mode or something. no power what so ever, and the damn thing is cutting out after i get past 45k rpms. read the codes on it and it came up with p0420, and it had about 6 or so other codes but they were just straight 0's, wouldnt tell me what they were. thinking it could be a clogged cat maybe? its got a loud pipe on it and all you can hear is engine, almost like nothings coming out of the exhaust but it is. tried repacing the fuel filter, changing the oil when it didnt really need to be, ran a can of sea foam through it, some 93 octane gas and some injector cleaner and still have nothing. anybody got any ideas?