sometimes my 94 xj has no power but seems to rev up fine.this doesnt happen all of the time though.i checked my exhaust system and the front of my muffler is broken and the pipe is loose inside of it(the muffler appears to be pretty new)im suspecting the cat or maybe the broken pipe is getting blocked somehow.if the cat was clogged or if the pipe was blocked wouldnt the check eng lite come on?my codes are all clear and the chk eng lite has never come on but it does work