I recently replaced my failed stock cat in my 98 Accord I4 with a "high flow cat" off Ebay (yes, I know it's a resonator and regret buying it but it was a quick, cheap replacement). This peice did not come with a bung for the o2 sensor so I also purchased an o2 simulator.
My question is.....am I better off ditching the resonator and o2 sensor for a different cat or will I be able to get by without too many problems with these products. Right now I am running no secondary o2 sensor and no o2 simulator and my gas mileage is absolutely horrible. I also understand that this is not a long term solution to this problem However, I'm looking at spending an upwards of $300 for a high flow cat from someone like Random Technology. Suggestions?

TIA for any help