i really need help with this

[terrelljames91]

i picked up a 88 rx7 that sat for 5 years through luck got it running, how ever it had a problem ideling, it was really rough and had popping in the exhaust(im assuming backfire?) anyway i figured a little bit of seafoam could help it, so i put some into it shut it off waited about 10-15 min, started it(extreamly hard) anyway now it sounds so quiet, almost like its running on one cylinder? and also i smelt burining, looked under the car and the catalytic and about a foot back was glowing BRIGHT red, is this a clogged cat? i really need help so any input would be very helpfull