New MG TF owner - Intermittent Blowing Exhaust NOise

I picked up a 2002 1.8 TF with 52k miles last weekend. My dad has had a TF for a few years now and i've been trying to buy it from him as he barely uses it but he was having none of it so I had to buy my own. I was told it had a bit of an exhaust blow by the previous owner before I bought it so its something I was aware of, the check engine light is also on. I drove the car 150 miles back home without any issues at all other than the slightly loud exhaust when accelerating (it sounds fine when the car is cruising).

I jacked the car up next day so I could have a look at the flexi section of the exhaust and when the the engine was started the blowing exhasut sound had gone, i'd had a look at all the sections of the exhaust system I could get to under the car and can't find any sections that are leaking. I've put the car back down on its wheels and started it up again and the blowing noise is still gone. As it was getting on in the day and I was losing light I had to give up on it for the day so haven't been able to look any further into it.

Does anyone have any suggestions as to what this could be? I'm going to take the car out for a short drive at the weekend to see if the noise comes back. Could worn or broken gearbox / engine mounts cause this if the engine is able to flex slightly and put pressure on the exhaust ssytem joints possibly opening them up slightly?

I'm also not sure if the head gasket has been done. The car runs fine, it didn't lose any coolant when I drove it home and there no mayo in the coolant or on the oil filler cap. Is it worth replacing the head gasket as a precaution or just leave it until theres an isue and it actually needs replacing?

There was a period when the tf had an actuator in the off side tail pipe operated by vacuum created by the inlet manifold (I think, citation required). Most of these must be time expired by now, however it may be worth squinting up your tail pipe.
The supposed function was to reduce noise by closing off the pipe over a certain rev range to placate some legitative body.
I have no firsthand experience of these other than seeing the occasional one on a scrapper but it could be worth exploring.

With regard to the HG, if it ain't broke don't fix it.......

My exhaust has the actuator on the off side outlet, when the revs reach about 2000rpm it opens to allow full flow! It does make the exhaust more throaty! But as it works fine so I haven't touched it.

If you can't see or hear a blow, I wouldn't worry to much. The giveaway for a blowing exhaust (if you can't see any obvious holes) would be soot or exhaust residue around joints, best checked when the exhaust is at working temperature (ie after a drive) as then metal will have expanded causing any obvious leaks to become apparent.

Hope that helps.

I was aware of the actuator fitted to the exhaust, but as both exhasut outlets are working when the car is at idle i assume its either been removed, is stuck open or was never fitted in the first place.

I've just bought a OBD2 reader so hopefully I can find out whats causing the engine management light to be on and get that sorted and I plan to have a ferret around under the car this weekend to investigate the exhaust blowing noise a bit further.

Thanks for the help.

Check the manifold to engine, if any work has been done it may be loose, happened to me.

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