I've been doing some research and I'm thinking this is ignition coils, but it seems to be slightly different from other people's problems, so here goes:

The SES light is on, and I had it read in the past and the PO420 came up, but they reset it and it went off, and recently came back on.

The most noticable problem is if I hold the RPM's at 1500-2000 the RPM's will begin to bounce up and down about 400 RPM. (for example if it's at 1800, every second or so the RPM's will drop to 1400, and this will repeat as long as I want to listen to it) It also becomes a problem during acceleration, as when I hit about 1800 RPM the car will begin to jerk/shake violently.

I was messing with it this afternoon, and sounds like there is a small exhaust leak (probably a result of y-pipe bolts coming loose) It is noticable because when the RPM bounce thing happens when I am parked in neutral, I hear a whistling noise every time the RPM's drop.

I also checked back at the muffler, and there is a very noticable drop in exhaust flow followed by what seems to be a very quiet backfire every time the RPM's drop.

Also during hard acceleration at about 3500-4000 RPM's I notice a power loss....it almost feels like when in my old 4 cyl Honda Accord I'd be accelerating and switch the A/C on. It's not a huge power loss, but definitely noticabkle.

So, is it ignition coils? Or something else? Your help is appreciated.

 

MAF in my opinion

 

Have you read it again to make sure it's still the same code? P0402 is a catalyst fault (usually O2 sensor going).

 

I haven't had it read again....I thought PO420 was the ignition coil code???

 

Nope, "Catalyst system fault - Right Bank". The most common ignition coil codes are P1320 (ignition signal primary circuit fault), P0300 (multiple cylinder misfire detected), and P0301 thru P0306 (misfire detected in cylinder #). A bad upstream O2 sensor can definitely cause the types of problems your detecting since it's used by the ECU to help adjust the air/fuel mixture.