Less Smoke - Less Poke?

[C.A.R.]

I'm confused.

My car runs a 125 map and Hoffman straight-through with decat. It used to smoke quite a lot (visibly in 3rd gear) when you were accelerating up to speed. Of late, the smoke has cleared. It doesn't seem to be any more / less economical, but the good old 'bum dyno' gives me the impression that it's not as quick as it was about a month ago.

No warning lights or anything on the dash. Could there be a ghost code in there anyway? Worth plugging in to check?

I'm just wondering what I can do. Some posts suggest un-plugging the MAF, will this cause erratic running? Should I try disconnecting it for the drive home ( ~ 17miles) or is that not a good idea?

New rattle started last week I'm convinced is a heatsheild beneath the gear selector, which is unrelated I hope. I'm now curious as to whether it could be the downpipe leaking though? Although I'd notice the noise surely? It doesn't sound like it's blowing.

What's the chances of the exhaust being blocked? As that's how it feels, almost like I'm being restricted a bit. Can't get under the car til the weekend...