My friend just bought an 88 crx si but it seems to be holding back on some power. He changed the oil, spark plugs, cap and rotor, and fuel filter. The car runs fine but it seems to be weak in the lower rpm, and a little just before the redline. I know this because we have two crx's that are exactly the same and both completely stock except for an intake. Someone told me it can be that the cat is clogged. Could that be our problem or is it something else?