92 VX de-aftermarketing

[Jughead]

I have this 92 Civic VX which I bought from a 17 year old kid who wrecked it and had to get rid of it. He pitched the OEM intake and swapped it for the typical K&N on a chrome tube. He also swapped out the ECU with one from a 1.6 V-TEC so that it would hit at about 5700 rpm. I am in the process of trying to get the car back to the way it should be. Who tries to trick out a 92 horsepower motor?? I mean come on. Anyway, I found the correct ECU on ebay (P07-A00) and plugged it in thinking it would fix the engine light and bring the V-TEC back down to where it should be. It did that and more. There is an upshift light!!! I was thinking all was well untill I got it out on the highway and when I was trying to maintain about 60mph the engine bogged down just like someone turned the key off. If I push the accelerator down it springs right into action as if it had no difficulty. If I let off and depress the clutch it comes down and Idles just fine. I tried just holding the pedal stationary and it boggs down lower and lower untill that throttle position is accelerating (hope thats clear?) then it accelerates fine. After reading a bit about the LAF and the 5 wire sensor I am wondering if it doesnt have something to do with that "lean burn". My question is what would cause the car to bog like it does at maintain speed? I currently have the non-VX ECU in it because the engine light is not as big of a deal as the bogging on the highway and I still average about 43-47mpg city and at 75mph for 1000 miles I netted 52 mpg on 89 octane 10%ethanol.

Any usefull info would help and be much appreciated.